The Texas Rangers signed Pérez in 2007 for $580,000 as an undrafted free agent. While only making 15 short starts in 62 innings at Rookie-level Spokane, Pérez went 1-2 with a 3.65 earned run average. Baseball America ranked Pérez as the #17 baseball prospect in their top 100 for 2010. On June 26, 2012, Pérez was called up by the Rangers. The next day he made his first major league appearance against the Detroit Tigers. He gave up 2 hits and 4 runs while striking out one over two-thirds of an inning. On June 30, Pérez made his first major league start, pitching 5 and a third innings and striking out five while only giving up two runs in a 7-2 win over the Oakland A's. On August 1, Pérez was optioned to Triple-A Round Rock to make room for pitcher Ryan Dempster. Pérez went into 2013 spring training competing for the fifth spot in the Rangers rotation, but on March 3 in a start against the Mariners, he broke his pitching forearm when it was hit by a linedrive byBrad Miller. After making 4 rehab starts, Pérez was recalled to make a start on May 27 in a double-header against the Diamondbacks. In his season debut, he went 5.1 innings, giving up 4 runs on 9 hits with 2 strikeouts. After the game, he was optioned to Round Rock. After 4 starts at Round Rock, he was recalled on June 22 to replace Josh Lindblom in the rotation. Pérez threw his first complete game on August 11 against the Astros. In 20 starts with the Rangers, Pérez went 10-6 with a 3.62 ERA, striking out 84 in 124.1 innings. On November 7, 2013, Pérez signed a four-year, $12.5 million contract with the Rangers that holds three club options, keeping him under team control through 2020. He received a $1 million signing bonus, and was to earn $750,000 in 2014, $1 million in 2015, $2.9 million in 2016, and $4.4 million in 2017. The 2018 option was worth $6 million and had a $2.45 million buyout. The 2019 option was worth $7.5 million and had a $750,000 buyout. The 2020 option is worth $9 million and has a $750,000 buyout. On April 23, 2014, Pérez threw nine shutout innings against the Oakland A's to secure his second consecutive complete game shutout. After several ineffective starts following the shutouts, Pérez was placed on the disabled list due to inflammation in his pitching elbow. On May 19, 2014, Pérez underwent Tommy John surgery to repair a partially torn UCL in the aforementioned elbow, which kept him out of action for the remainder of 2014. Pérez began the 2015 season on the 60-day disabled list to continue recovery from Tommy John surgery. Pérez had his first major league hit on July 15, 2016, against Chicago Cubs' pitcher Kyle Hendricks. He hit a single to Kris Bryant. He had been hitless his first nine at bats. In 2016 he was 10-11 and had the fewest strikeouts per 9 innings in the major leagues. He had more batters reach base against him on errors, 16, than any other pitcher in the major leagues. In 2017 he was 13-12 with a 4.32 ERA, and had the highest WHIP among major league pitchers. He also had the highest line drive percentage allowed of all major league pitchers. On April 30, 2018, Pérez was placed on the disabled list with discomfort in his right elbow. He was activated on July 14, replacing Alex Claudio, who was placed on the DL. In 2018 he was 2-7 with a 6.22 ERA.
Minnesota Twins
On January 30, 2019, Pérez signed a one-year contract with the Minnesota Twins. He was expected to compete for the fifth spot in the starting rotation. During the 2019 season, he made 32 appearances with 29 starts, with a WHIP of 1.52, the highest in the major leagues. He compiled a 10–7 record in innings pitched.
Boston Red Sox
After becoming a free agent following the 2019 season, Pérez signed a one-year contract with the Boston Red Sox on December 19, 2019; the contract also included a team option for the 2021 season.
