Minor leagues The
New York Yankees selected Kennedy in the first round, 21st overall, of the
2006 Major League Baseball draft. He was the 39th player in USC history to become a first-round MLB draft selection. He signed with the team in mid-August for a $2.25 million
signing bonus, roughly $750,000 more than expected for a 21st overall draft selection, and was assigned to the
Class A Short-Season Staten Island Yankees of the
New York–Penn League. Kennedy made his professional baseball debut on September 6, 2006, pitching innings against the
Tri-City ValleyCats. After playing one game for Staten Island, Kennedy spent the winter with the
West Oahu CaneFires of the
Hawaii Winter Baseball league. In nine games there, including seven
starts, he posted a 0–2 record and a 4.45 ERA, striking out 45 batters in innings. In 10 Class A starts, Kennedy posted a 6–1 record with a 1.29 ERA, striking out 72 batters in 63 innings and holding his opponents to a .183
batting average. He received a promotion to the
Double-A Trenton Thunder at the start of June and won his Double-A debut against the
Binghamton Mets on June 6, 2007. On July 24, Kennedy and his rotation mate
Joba Chamberlain were both promoted from Trenton to the
Triple-A Scranton/Wilkes-Barre Yankees. At the time of his promotion, Kennedy led the Yankees'
farm system with 129 strikeouts and was tied for first with 11 wins. He made only six starts with Scranton, going 1–1 with a 2.08 ERA and striking out 34 batters in innings. Altogether, Kennedy posted a 12–3 minor league record in 2007, with a 1.91 ERA and 163 strikeouts in 25 starts and innings.
New York Yankees (2007–2009) After
Mike Mussina lost three starts in a row for the Yankees, recording a 17.69 ERA in the process, Kennedy was called up to take his spot in the rotation at the end of August, becoming the second Yankee that season to climb from Class A to major league ball. He made his major league debut on September 1, 2007, allowing only one
earned run in seven innings of an eventual 9–6 victory over the
Tampa Bay Devil Rays. After going 1–0 with a 1.89 ERA in his first three major league starts, Kennedy had to be scratched from a scheduled September 22 game against the
Toronto Blue Jays because he strained a muscle in his upper back. The injury forced Kennedy to miss the remainder of the season. The plan did not work as expected: Kennedy went 0–2 with an 8.37 ERA in his first six games and was optioned to Triple-A on May 4, with
Darrell Rasner taking his place at the back of the rotation. After finding success in the
International League, including a four-game stretch with a 1.33 ERA, Kennedy was called back up to the Yankees for an emergency start against the
Los Angeles Angels of Anaheim on August 8. He allowed nine hits and five runs and was pulled out of the game in the third inning. Kennedy's major league record for the season fell to 0–4 while his ERA rose to 8.17. It would be his last major league start in the Yankees organization. Kennedy opened the 2009 season in Triple-A but began feeling numbness in his pitching hand that April. On May 8, he was diagnosed with an
aneurysm around his biceps and underwent surgery the following week. He began facing live batters again at the start of September, and from there, Kennedy pitched in six minor-league games, including two starts, for a total of innings. He returned to the major leagues on September 20, with manager
Joe Girardi intending to utilize Kennedy as a
long reliever. Kennedy made his first Yankees appearance in over a year on September 23, walking two batters and hitting another with a pitch during the eighth inning of an eventual 3–2 win over the Angels. Kennedy was subsequently left off of the postseason roster on the Yankees' run to a
2009 World Series championship title.
Arizona Diamondbacks (2010–2013) On December 8, 2009, Kennedy was part of a three-team, seven-player trade with the Yankees,
Arizona Diamondbacks, and
Detroit Tigers. Kennedy,
Phil Coke, and prospect
Austin Jackson went from New York to Detroit in exchange for All-Star center fielder
Curtis Granderson, with Kennedy then flipped to Arizona alongside
Edwin Jackson so that the Tigers could acquire Diamondbacks pitchers
Max Scherzer and
Daniel Schlereth. The Diamondbacks started showing interest in Kennedy when he pitched for the Arizona Fall League, and he earned a position in the Arizona starting rotation by the end of March 2010. The Diamondbacks' player development staff agreed at the start of the season to limit Kennedy's workload to a total of 180 innings, an amount that would help the pitcher extend his durability without pushing him into additional injuries. Kennedy picked up his first win in over two years on April 29, pitching eight innings in the Diamondbacks' 13–5 rout of the
Chicago Cubs. Kennedy was able to take a one-run game into the eighth inning before giving up a
grand slam to
Kosuke Fukudome, and
Daniel Stange was called in to pitch a perfect ninth inning for his own MLB debut. On August 26, Kennedy struck out a career-high 12 batters in an 11–5 victory over the
San Diego Padres. He cited Arizona's early lead, in which they picked up nine runs in the first innings, with helping him relax enough to maintain his command. Kennedy finished his first full major league season with a 9–10 record and a 3.80 ERA in 32 starts, as well as 168 strikeouts in 194 innings. He also walked 70 batters and led MLB with 16
wild pitches. Arizona manager
Kirk Gibson tapped Kennedy to serve as the Diamondbacks' opening day starter for the
2011 season, after he went 0–0 with a 7.88 ERA during spring training. Kennedy took two innings to settle into his rhythm, allowing three earned runs in six innings of the eventual 7–6 loss to the
Colorado Rockies. After a brief trip to New York to be with his wife and their newborn child, Kennedy pitched his first major league
complete game on April 25, outdueling ace
Cliff Lee in a 4–0 shutout of the
Philadelphia Phillies. He continued to perform well through the summer, building a seven-game winning streak as well as 22 straight starts in which he threw at least 100 pitches. Both of those streaks were broken on August 19, when Kennedy allowed three runs and five hits to the Phillies in three innings. With an eight-inning outing in the 1–0 defeat of the
Pittsburgh Pirates on September 19, Kennedy became the first
National League pitcher that season to reach 20 wins. Kennedy finished the season with 21 wins, tying Cy Young honoree
Clayton Kershaw as the
NL win leader. He also ranked among the leaders in the NL with 198 strikeouts, a 2.88 ERA, and 222 innings pitched. Additionally, at no point during the 2011 season did Kennedy lose two or more consecutive starts. Kennedy finished fourth in voting for the 2011 NL Cy Young Award, behind Kershaw,
Roy Halladay, and
Cliff Lee. The Diamondbacks' banner season echoed Kennedy's: after finishing last in the
NL West during the 2010 season, Arizona clinched the NL West title with a 3–1 victory over the
San Francisco Giants on September 23. Kennedy was called upon to start Game 1 of the
2011 National League Division Series against the
Milwaukee Brewers, pitching opposite
Yovani Gallardo. He was unable to carry his regular season success into the playoffs, giving up four earned runs in innings and taking the loss in the 4–1 defeat. Kennedy faced Gallardo again in game 5, with neither pitcher taking the decision. While
John Axford's first blown save for the Brewers took the game into
extra innings, the Diamondbacks were eliminated on a walk-off RBI from
Nyjer Morgan. Kennedy picked up his first opening day win in 2012, outpitching Giants ace
Tim Lincecum in a 5–4 victory. He struggled early in the season, with a 3–5 record and 4.65 ERA by the start of June, but felt "like [he] got in a nice little groove" against the Giants on June 1, allowing only one run in innings. In his next start, after making a "secret" mechanical change to his pitches, Kennedy matched his career high 12 strikeouts in a 10–0 shutout of the Colorado Rockies. That July, he lasted eight innings in two consecutive starts, giving up three runs across the 16 total innings. In the second start, Kennedy also hit his first career
triple, clearing the bases in a 6–3 defeat of the Rockies. While his record and ERA dropped to 14–11 and 4.14 during the 2012 season, respectively, Kennedy boasted an 8.0 K/9 ratio for the second year in a row, and maintained a 2.0
Wins Above Replacement for the year. Kennedy once again served as Arizona's opening pitcher for the 2013 season, striking out eight batters and allowing two runs in seven innings of a 6–2 defeat of the St. Louis Cardinals. On June 11, while facing the division rival
Los Angeles Dodgers, Kennedy accidentally glanced a fastball off of
Yasiel Puig's face in the sixth inning. In the next inning, Dodgers starter
Zack Greinke retaliated by striking catcher
Miguel Montero in the back. In the bottom half of that inning, Kennedy struck Greinke in the helmet with a pitch, leading to a
benches-clearing brawl between the Dodgers and Diamondbacks, with six players and coaches ejected from the game. Kennedy was suspended for 10 games for what MLB referred to as "intentionally throwing a pitch in the head area of Zack Greinke ... after a warning had already been issued to both clubs". At the time of his suspension, Kennedy was 3–4 with a 5.21 ERA. He returned on June 29, where control problems led to four runs in innings and Arizona extended its losing streak to 21 games.
San Diego Padres (2013–2015) On July 31, 2013, the Diamondbacks traded Kennedy to the
San Diego Padres in exchange for relief pitcher
Joe Thatcher, relief prospect
Matt Stites, and a compensatory pick in the upcoming draft. Padres general manager
Josh Byrnes was also the Diamondbacks' general manager when they had acquired Kennedy prior, and he referred to the pitcher as "the first guy I have ever traded for twice". The Padres immediately added Kennedy to their starting rotation, where he joined
Andrew Cashner,
Tyson Ross,
Eric Stults, and
Edinson Volquez. After being traded, Kennedy struggled on the road, going 0–2 in his first four away starts with a 6.95 ERA. In his worst outing of the season, Kennedy allowed six runs on eight hits in innings against the
Pittsburgh Pirates. He posted a 4–2 record and a 4.24 ERA in 10 games with San Diego that season, striking out 55 batters in innings. On May 9, while facing the
Miami Marlins, Kennedy not only tied his career-high 12 strikeouts as a pitcher, but he hit the first home run of his career, a solo shot against Miami starting pitcher
Jacob Turner in the sixth inning. Over the course of the season, Kennedy saw noticeable improvement in his ERA,
walks plus hits per innings pitched (WHIP), and strikeout-to-walk ratio over the previous season, which he credited to Black and pitching coach
Darren Balsley, the latter of whom taught Kennedy to strengthen his leg kick when pitching to improve his command. Balsley's advice helped Kennedy add an extra mile per hour of velocity to Kennedy's fastball, which now reached speeds of and helped him strike out an average of 9.27 batters per nine innings. On September 27, while facing the
San Francisco Giants for his 33rd and final start of the season, Kennedy passed his 200th inning pitched of the season for the third time in his career, and struck out his 200th batter of the season for the first time. He finished the year with a 13–13 record and a 3.63 ERA. While starting the Padres' 2015 home opener against the Giants, Kennedy had to be taken out of the game in the third inning with a left hamstring strain. He explained later that he had begun to feel pain in the area on the final pitch of the second inning, and that he had asked to be taken out to avoid injuring his arm by altering his pitching mechanics. He returned on April 25 to face the
Los Angeles Dodgers, giving up eight hits and eight runs in innings while striking out only two batters. The injury set Kennedy off-course at the start of the season, and by the end of May, he had a 7.15 ERA in eight starts. He recovered through the middle part of the season, striking out 93 batters in 16 starts between June and August while holding his opponents to a .229 batting average, but struggled again at the end of the year. In his final six starts of 2015, batters hit .297 against Kennedy, who had a 5.61 ERA in that span. He finished the year with a 9–15 record and a 4.28 ERA but showed considerable improvement in his fastball velocity and in his K/9 ratio, the latter of which was 9.3 for the year.
Kansas City Royals (2016–2020) On January 16, 2016, the
Kansas City Royals signed Kennedy to a five-year, $70 million contract, with an opt-out clause built in prior to the 2018 season. Kennedy was happy to join the team, which he described as "an easy environment", and particularly enjoyed the reunion with his Yankees pitching coach,
Dave Eiland. On the final day of spring training, Kennedy exited the mound shortly before the fourth inning with left hamstring tightness. Manager
Ned Yost said that the removal was precautionary for a "slight" injury. Kennedy later took the win in his Royals debut, striking out seven batters in innings in a 7–0
shutout of the
Minnesota Twins. The Royals could not keep apace of their previous World Series-winning season, however, and on July 25, Kennedy managed to load the bases within six minutes of the first pitch of the game, putting the Royals in a 4–0 deficit out of the gate. He followed this effort by allowing only three runs in four starts, but was not credited with a win between June 26 and August 15. The drought was ultimately broken when Kansas City defeated Detroit 3–1. While Kennedy was mostly happy with his performance during the 2016 season, in which he went 11–11 with a 3.68 ERA and struck out 184 batters in innings, he was disappointed that the Royals did not reach the postseason, and his 33 home runs allowed were "a lot more" than he had been "expecting or hoping for". At the start of the
2017 MLB season, Kennedy served as the Royals' No. 2 starter, behind former reliever
Danny Duffy. After going 0–3 with a 3.03 ERA in his first six starts, Kennedy suffered another hamstring injury on May 4, leaving the mound against the
Chicago White Sox after innings. He returned on May 21, lasting only two innings while walking three batters and giving up a pair of home runs. Kennedy and manager
Ned Yost both clarified that the pitcher felt physically fine, and that his command issues were mental. Ultimately, however, the hamstring injury continued to bother Kennedy through the remainder of the season, particularly when he tried to utilize his
changeup, historically Kennedy's most effective approach. His 5.38 ERA for the year was Kennedy's worst since 2008, and after returning at the end of May, his opponents boasted a .528
slugging percentage against him. Despite struggling his way to a 5–13 record for the year, Kennedy chose not to opt out of the remainder of his Royals contract, saying that it "would be pretty stupid" to forego the final three years of the agreement. A number of injuries befell Kennedy during the
2018 season. On April 24, he was hit in the foot with a line drive off the bat of
Ryan Braun of the
Milwaukee Brewers. Kennedy was able to finish pitching the inning but had to be removed from the game afterwards with a contusion. It was the first time in Kennedy's 274 major league starts that he had not recorded at least one strikeout. Most of Kennedy's summer was taken up with a left oblique strain: he was originally put on the 10-day disabled list for the injury at the end of June, with a return date of July 10. During that attempted start, Kennedy lasted only three innings before a recurrence of the oblique strain forced him off the mound and back onto the disabled list. Kennedy returned to the mound in full on September 9 to pitch six innings against the
Minnesota Twins. Injuries limited Kennedy to only 22 starts for the year, in which he went 3–9 with a 4.66 ERA and struck out 105 batters in innings. Kennedy himself was hesitant to make the change, believing that he was capable of another year in the starting rotation, but he ultimately had a successful stint as the Royals'
closer. On July 28, Kennedy recorded his 20th
save of the year, becoming the sixth pitcher since saves were recorded in 1969 to compile 20 wins and 20 saves in a single season. For the period between May 30 and September 23, Kennedy led MLB with 28 saves, including 19 after the All-Star break, and he noticed a physical improvement to becoming a reliever, in contrast to feeling "like you get hit by a truck every fifth day" as a starting pitcher. On August 15, Kennedy made his first starting appearance since 2018, pitching the first two innings of a bullpen game against the
Minnesota Twins. At the end of the month, he was placed on the
injured list when he suffered a left calf strain in the ninth inning of a game against the
Chicago White Sox. Kennedy attempted to field a ground ball but began limping afterwards and had to be removed from the game. The injury limited Kennedy to only 15 appearances during the truncated season, during which he posted a 9.00 ERA and a 1.786 WHIP. When Texas released their opening day roster on April 1, Kennedy and fellow spring training invitee
Matt Bush were both named to the 25-man roster. The oldest member of the Rangers' bullpen by three years, Kennedy entered the season expecting to serve as the team's
setup man, but a series of season-ending injuries to Bush,
José Leclerc, and
Jonathan Hernández forced the team to turn to Kennedy as their closer. By May, Kennedy had secured nine saves in nine attempts, giving the Rangers the most saves in the American League. As the season progressed, the Rangers rarely held leads late into games, and they had less use for Kennedy as a closer. At the start of June, he had a brief stint on the injured list for a strained hamstring. In his half-season with the Rangers, Kennedy posted a 2.51 ERA and a 1.05 WHIP in 32 appearances, while successfully converting 16 saves in 17 opportunities.
Philadelphia Phillies (2021) Kennedy was part of a trade deadline package deal on July 30, 2021, that sent him, starting pitcher
Kyle Gibson, prospect
Hans Crouse, and cash considerations to the
Philadelphia Phillies in exchange for pitcher
Spencer Howard and prospects
Kevin Gowdy and Josh Gessner. The Phillies, who had been struggling with both an unreliable bullpen and an injury-riddled starting rotation, acquired Kennedy hoping he would serve as a dependable closer. This allowed acting closer
Ranger Suárez to join the rotation.
Arizona Diamondbacks (second stint) On March 16, 2022, Kennedy signed a one-year contract with a mutual option for 2023 with the
Arizona Diamondbacks. Kennedy made 57 appearances for the Diamondbacks in 2022, struggling to a 4–7 record and 5.36 ERA with 44 strikeouts in 50.1 innings pitched. On November 8, the Diamondbacks declined their half of a $4 million mutual option and Kennedy entered free agency.
Texas Rangers (second stint) On January 27, 2023, Kennedy signed a minor league contract with the
Texas Rangers organization. On March 29, it was announced that Kennedy had made the Opening Day roster, and his contract was selected to the 40-man roster. He made 11 appearances for the Rangers, registering a 7.20 ERA with 13 strikeouts in 10.0 innings pitched. On May 11, Kennedy was designated for assignment. He cleared waivers and was sent outright to the Triple-A
Round Rock Express on May 14. However, Kennedy rejected the assignment and instead elected free agency. On June 20, 2023, Kennedy re–signed with the Rangers on a minor league contract. After posting a 3.51 ERA in 22 games for Triple–A Round Rock, he was selected back to the major league roster on September 5. On September 16, Kennedy was placed on the 60–day injured list with a right
rotator cuff strain, ending his season.
Retirement Kennedy announced his retirement from professional baseball on November 2, 2023, shortly after winning the World Series with Texas. In 497 games across 17 MLB seasons, Kennedy finished his career with a 104–114 record and a 4.16 ERA. == Pitching style ==