Minor leagues Philadelphia Phillies Simón was signed on July 9, 1999, by the
Philadelphia Phillies. He originally signed under the name Carlos Cabrera, and he pretended to be 21 months younger than he really was. He made his professional debut in 2000 for the La Vega Phillies in the
Dominican Summer League. In 2004, the Phillies found out his real name and age.
San Francisco Giants On July 30, 2004, Simón was traded with
Ricky Ledée to the
San Francisco Giants for
Felix Rodríguez. Simón was assigned to the Single-A
San Jose Giants. He got off to a bad start, posting a 5.68 ERA in six starts while going 1–2. In 2005, he was promoted to the Double-A
Norwich Navigators. He started for only part of the year, and closed for most of the season, going 3–8 with 19 saves while posting a 5.03 ERA in 43 games (nine starts). On March 17, 2007, the Phillies returned Simón to the Rangers. Simón pitched as a starter for the Triple-A
Oklahoma RedHawks. He had a bad year, going 5–10 with a 6.43 ERA in 22 starts. He was released on March 30, before the season started.
Mexican League After being released, Simón signed with the independent
Sultanes de Monterrey of the
Mexican League. He pitched very well with them, going 7–2 with a 2.67 ERA in 15 games (11 starts).
Major leagues Baltimore Orioles The Orioles originally assigned Simón to the AAA
Norfolk Tides, but they quickly called him up. On September 6, he made his MLB debut. He finished 2008 with a 6.23 ERA in four games (one start) and no decisions. However, he was injured in only his second start and missed the rest of the year after undergoing
Tommy John surgery. Simón failed to make the Orioles out of spring training in 2010, but on April 27, the Orioles promoted Simón from Triple-A Norfolk. The same day, he became the Orioles' closer (due to bad pitching and a subsequent injury to
Mike Gonzalez), and he notched his first
save against the
New York Yankees. He pitched an inning and gave up no earned runs (and two unearned). Coincidentally, the Yankees were the same team Simón earned his first decision against. Simón converted his first five save opportunities before blowing one against the
Cleveland Indians on May 15. In 49 relief appearances, Simón was 4–2 with a 4.93 ERA while converting 17 of 21 save opportunities.
Cincinnati Reds On April 3, 2012, the
Cincinnati Reds claimed Simón off waivers from the Orioles. He served in the bullpen for the season, posting a 3–2 record with one save and a 2.66 ERA in 36 games. On July 13, 2014, Simón was named to the
2014 Major League Baseball All-Star Game, replacing fellow Red
Johnny Cueto, who was unavailable to pitch due to starting a game the previous Sunday. Simon was mobbed by his teammates in the dugout when the announcement was made during the game. In the All-Star game, Simón pitched a scoreless third inning, allowing one hit and striking out one batter. He would win only three more games after the All-Star break, finishing at 15–10 with a 3.44 ERA in 32 starts, while throwing a career-high innings. On January 16, 2015, Simón and the Tigers avoided arbitration when the two parties agreed on a one-year contract worth $5.5 million. On August 20, 2015, Simón recorded his first career
complete game shutout in the Tigers 4–0 win over the
Texas Rangers. He allowed only one hit in the contest, a double to
Rougned Odor in the fifth inning, while walking two and striking out five. Despite finishing the season with a league-worst 5.05 ERA, Simón led the Tigers in wins (13) and innings pitched (187).
Long Island Ducks On June 6, 2017, Simon signed with the
Long Island Ducks of the
Atlantic League of Professional Baseball. He became a free agent after the 2017 season. In 12 games (9 starts) he threw 55.1 innings going 2-3 with a 4.55 ERA with 48 strikeouts, 1 save and also throwing one complete game shutout.
Tigres de Quintana Roo On July 3, 2018, Simon signed with the
Tigres de Quintana Roo of the
Mexican Baseball League. He was released on August 16, 2018. In 16 games 19.1 innings of relief he went 1-0 with a 2.33 ERA with 17 strikeouts and 4 saves.
Acereros de Monclova On June 25, 2021, Simón signed with the
Acereros de Monclova of the
Mexican League. Simón allowed three runs without recording an out in his only appearance with Monclova, and was released by the team the next day. ==Pitch selection==