Pre-draft On December 31, 2014, Alexander announced on his
Twitter account his decision to forgo his senior season and enter the 2015 NFL draft. Alexander was one of 33 collegiate linebackers to attend the
NFL Scouting Combine in
Indianapolis, Indiana. Alexander completed all of the necessary drills, finishing second among all linebackers in the
40-yard dash, sixth in the
bench press and
short shuttle, and ninth in the
three-cone drill. On March 27, 2015, Alexander attended LSU's
pro day, but opted to stand on his combine numbers and only performed positional drills for team representatives and scouts from all 32 NFL teams, including
Pittsburgh Steelers' head coach
Mike Tomlin and general managers from the
Minnesota Vikings,
New Orleans Saints,
New York Giants,
New York Jets, and Steelers. During the draft process, he attended only one private visit with the
San Francisco 49ers. At the conclusion of the pre-draft process, Alexander was projected to be a third round pick by
NFL draft experts and scouts. He was ranked the second best outside linebacker prospect in the draft by NFL analyst
Charles Davis, was ranked the sixth best outside linebacker in the draft by NFLDraftScout.com, and was ranked the seventh best linebacker by Matt Miller of NFLDraftScout.com.
Tampa Bay Buccaneers in 2015
2015 season The
Tampa Bay Buccaneers selected Alexander in the fourth round (124th overall) of the 2015 NFL draft. The Buccaneers traded their fourth (128th overall) and seventh round (218th overall) picks to the
Oakland Raiders in order to move up four spots and select Alexander. He was the 11th linebacker drafted in 2015. On May 12, 2015, the Buccaneers signed Alexander to a four-year, $2.75 million contract that includes a
signing bonus of $478,322. Alexander entered training camp, competing for the job as the starting strongside linebacker against
Danny Lansanah. After performing well, he was moved to middle linebacker to compete for the starting role against veteran
Bruce Carter. Head coach
Lovie Smith named Alexander the starting middle linebacker alongside outside linebackers
Lavonte David and Lansanah. Alexander made his NFL debut and first NFL start in the season-opener against the
Tennessee Titans and recorded five combined tackles and a pass deflection during a 42–14 loss. Two weeks later, he recorded ten combined tackles, two pass deflections, and made his first NFL
interception off of a pass attempt by
Ryan Mallett in a 19–9 road loss to the
Houston Texans. During Week 5, Alexander made five combined tackles, two pass deflections, and made his first NFL sack on
Blake Bortles as the Buccaneers defeated the
Jacksonville Jaguars by a score of 38–31. Prior to Week 8, Alexander's younger brother, Broderick Taylor, had been murdered just two days prior. He started the following game and recorded 11 combined tackles, a forced fumble, a fumble recovery, and an interception during a 23–20 road victory over the
Atlanta Falcons. His efforts earned him the title of NFC Defensive Player of the Week. On December 7, Alexander was given a four-game ban for violating the league's policy on performance-enhancing substances and missed the last four games of the season (Weeks 14–17). Alexander finished his rookie year with 93 combined tackles (59 solo), nine pass deflections, three sacks, and two interceptions in 12 games and starts. The Buccaneers finished fourth in the
NFC South with a 6–10 record and Lovie Smith was fired at the end of the season.
2016 season Offensive coordinator
Dirk Koetter was promoted to head coach and hired former Falcons head coach
Mike Smith as defensive coordinator. Smith retained Alexander as starting middle linebacker to begin the regular season. Alexander started in the season-opener at the Falcons and recorded 17 combined tackles and a sack in a 31–24 victory. Two weeks later, he made seven combined tackles and returned an interception off of
Case Keenum 38 yards for his first NFL touchdown during a 37–32 loss to the
Los Angeles Rams. During Week 8, Alexander recorded a season-high 14 solo tackles and broke up a pass in a 30–24 overtime loss to the
Oakland Raiders. During Week 15, he recorded a career-high 21 combined tackles (11 solo) in a 26–20 road loss against the
Dallas Cowboys. Alexander finished his second professional season ranking fourth in the league in tackles with 145 combined (108 solo). He also had seven pass deflections, three sacks, and an interception in 16 games and starts. He earned an overall grade of 77.3 from Pro Football Focus and was their most improved second-year linebackers.
2017 season Alexander started in the season-opener against the
Chicago Bears and recorded a solo tackle, a pass deflection, and intercepted former teammate
Mike Glennon during a 29–7 victory. He left the game after sustaining a
hamstring injury that sidelined him for the next four games (Weeks 3–6). In Week 15, Alexander recorded a season-high 13 solo tackles as the Buccaneers lost to the Falcons by a score 24–21. Alexander finished his third season with 97 combined tackles (70 solo), four pass deflections, and a career-high three interceptions in 12 games and starts. On January 16, 2018, he was named to his first
Pro Bowl replacing injured
Seattle Seahawks middle linebacker
Bobby Wagner.
Pro Football Focus gave Alexander an overall grade of 68.0, ranking him 48th among all qualifying linebackers in 2017.
2018 season Alexander started the first six games of the season before suffering a season-ending torn ACL in Week 7. He was placed on
injured reserve on October 22, 2018. Alexander finished the season with 45 tackles, two sacks, two pass deflections, and a sack in six games and starts.
San Francisco 49ers On March 13, 2019, the
San Francisco 49ers signed Alexander to a four-year, $54 million contract that includes a signing bonus of $4 million and $25.50 million guaranteed. During Week 1 against his former team, the
Tampa Bay Buccaneers, Alexander made a helmet-to-helmet hit against former teammate
Jameis Winston, and was disqualified as a result. Prior to being ejected, Alexander made three tackles in the season-opening 31–17 road victory. In the next game against the
Cincinnati Bengals, Alexander recorded his first interception of the season off of
Andy Dalton in the 41–17 road victory. During Week 7 against the
Washington Redskins, Alexander forced a fumble on running back
Adrian Peterson that was recovered by teammate
Jullian Taylor in the 9–0 road victory. Two weeks later against the
Arizona Cardinals, he left the eventual 28–25 road victory with an apparent chest injury. The next day, Alexander was diagnosed with a torn pectoral and was placed on
injured reserve. Alexander was designated for return from injured reserve on January 2, 2020, and began practicing with the team again. On January 10, 2020, the 49ers activated Alexander off injured reserve the day before the NFC Divisional Game against the Vikings. He helped the 49ers defeat both the Vikings and
Green Bay Packers to advance to
Super Bowl LIV, where he recorded a tackle and pass deflection in the 31–20 loss to the
Kansas City Chiefs.
New Orleans Saints On November 2, 2020, the San Francisco 49ers traded Alexander to the Saints in exchange for a fifth-round conditional pick in the
2021 NFL draft and linebacker
Kiko Alonso. He was named a starter in Week 10, and started the next seven games before suffering a torn Achilles in Week 16. He was placed on injured reserve on December 28, 2020. On March 16, 2021, the Saints released Alexander. On August 3, 2021, the New Orleans Saints brought back Alexander and signed him to a one-year, $1.12 million contract that includes a signing bonus of $387,500. He was placed on injured reserve on September 17, 2021, with an elbow injury. He was activated on October 25.
New York Jets On August 2, 2022, the Jets signed Alexander to a one year, $1.27 million contract that includes a signing bonus of $152,500.
Pittsburgh Steelers On July 30, 2023, the Steelers signed Alexander to a one-year, $1.31 million contract that includes a signing bonus of $152,500. On November 12, 2023, in the Week 10 game against the
Green Bay Packers, Alexander suffered a season-ending torn Achilles. Two days later, the Steelers placed him on injured reserve ending his season and subsequently his tenure with the Steelers.
Denver Broncos On September 25, 2024, Alexander was signed to the
Denver Broncos practice squad. In three games and two starts with the Broncos, Alexander recorded eight tackles and a forced fumble.
Detroit Lions On November 29, 2024, Alexander was signed by the
Detroit Lions off the Broncos practice squad. He was released on December 26, and re-signed to the practice squad. ==NFL career statistics==