Doubront was 17 years old when he entered the minors in 2005 with the VSL Red Sox, playing for them one year before joining the GCL Red Sox, Lowell Spinners, Greenville Drive and Lancaster JetHawks. His most productive season came in 2008, when he posted a combined 13–9 record with a 3.76 ERA in 119 ⅓ innings of work.
Boston Red Sox
Doubront made his Major League debut on June 18, 2010, against the Los Angeles Dodgers, pitching five innings, allowing three earned runs, two walks, and struck out two for the win. It was a spot start and Doubront was optioned back to Pawtucket after the game. He was recalled on July 5 after Clay Buchholz joined a long list of Red Sox players to go on the disabled list. Doubront made two more starts and lost both of them before being optioned on July 17. He was recalled August 6, and returned to the Red Sox roster as a reliever. Doubront entered the 2012 season as one of the Red Sox starters, beating out Aaron Cook and Alfredo Aceves in spring training. Despite slow starts for Josh Beckett, Clay Buchholz and Jon Lester, and Daniel Bard's demotion to the minors, Doubront earned five wins against two losses in his first ten starts. In June, Doubront took a no-hitter into the sixth inning against the Miami Marlins. He finished the game giving up two runs on three hits and earned the win. He ended the season as a full-time starter, with a record of 11-10. Doubront turned in another effective season in 2013, posting an 11-6 record over 27 starts for a Red Sox team that would win 97 games and a World Championship. Doubront pitched out of the bullpen in the postseason, earning his first career postseason victory in Game 4 of the 2013 World Series. Doubront struggled to start the 2014 season. In May, he left a game after experiencing discomfort in his left shoulder, later attributed to hitting it on a car door. He would later lose his spot in the starting rotation due to his inconsistency. He criticized the decision, stating "First of all, I’m not a reliever... They know that. They just, you know, it’s hard but I don’t know what they’re doing. I know they’re not doing the right thing for me." After allowing 6 runs in of an inning against the Toronto Blue Jays on July 28, Doubront had a meeting with manager John Farrell, and two days later he was traded. To begin the 2014 season, Doubront's record was 2-4 with a 6.07 ERA in 17 games.
Chicago Cubs
On July 30, 2014, Doubront was traded to the Chicago Cubs for a player to be named later. He was placed on the disabled list on August 1 without having pitched for the Cubs. He was activated from the disabled list on August 30. In 4 more starts, Doubront posted a 3.98 ERA with a 2-1 record. Overall in 2014, combined with both teams, Doubront's record was 4-5 with a 5.54 ERA in 21 appearances. The Cubs released Doubront on March 28, 2015.
Toronto Blue Jays
On April 2, 2015, Doubront signed a minor league contract with the Blue Jays, and was assigned to the Triple-A Buffalo Bisons. On May 13, he was activated off the disabled list and made his Bisons debut, pitching five shutout innings and allowing only one hit and one walk. Doubront was called up by the Blue Jays in early July, and made his debut for the team pitching 2 relief innings against the Detroit Tigers on July 3. He made his first start for the Blue Jays on July 7, pitching 6 innings and getting the win against the Chicago White Sox, 2–1. Doubront was designated for assignment on July 29. In 5 games, Doubront went 1-1 with a 4.76 ERA.
Oakland Athletics
On July 31, 2015, Doubront was traded to the Oakland Athletics for cash considerations. Finishing the season with the Athletics, Doubront made 11 appearances with a 2-2 record and a 5.81 ERA. Overall in 2015, his total record was 3-3 with a 5.50 ERA in 16 appearances. On April 11, 2016, it was revealed that Doubront would undergo Tommy John surgery and miss the entire 2016 season. Doubront was outrighted to the Triple-A Nashville Sounds on October 7, 2016, and he then elected free agency. In November 2016, Doubront re-signed with Oakland on a minor league contract. He elected free agency on November 6, 2017.
Lotte Giants
On December 14, 2017, Doubront signed a one-year, $1 million contract with the Lotte Giants of the KBO League. Doubront made just three starts and posted a 13.50 ERA in 9⅓ innings. Afterwards, he was placed on waivers in September 2018.
On February 14, 2019, Doubront signed with the Pericos de Puebla of the Mexican League. He was released on May 3, 2019.
Saraperos de Saltillo
On May 14, 2019, Doubront signed with the Saraperos de Saltillo of the Mexican League.
Scouting report
Doubront's main pitches are a four-seam and two-seam fastball that range between 90–95 mph. He also throws a cut fastball, a big curveball, and a changeup that is used mostly against right-handed hitters. His deceptive delivery results in hitters not being able to pick up the ball until late. The late pick-up also makes his fastball look faster to opposing hitters.
