Roberto Osuna

Osuna made his professional baseball debut with the Diablos Rojos del México of the Mexican League in 2011. In 13 appearances totaling 19⁄3 innings, he pitched to a 0–1 record, 5.49 earned run average (ERA), and 12 strikeouts.

In August 2011, Osuna was acquired by the Blue Jays for $1.5 million. He began the 2012 season with the Bluefield Blue Jays of the Appalachian League, but was promoted to the Vancouver Canadians of the Northwest League after posting a 1–0 record with a 1.50 earned run average in seven appearances (four starts). He made his Canadians debut on July 28, 2012, striking out a franchise-record 13 batters over five innings pitched. In total, Osuna pitched 43⁄3 innings in 2012, and posted a 2–0 record, 2.27 ERA, and 49 strikeouts.

On January 29, 2013, Osuna was ranked 90th on MLB's Top 100 Prospects list. He started the 2013 season with the Class-A Lansing Lugnuts of the Midwest League. On May 9, 2013, it was announced that Osuna had torn his ulnar collateral ligament, an injury that usually requires Tommy John surgery. He met with Dr. James Andrews, and was advised to rest and rehab the injury, rather than undergo surgery. Osuna returned from the disabled list on June 9, and pitched five shutout innings for Lansing. Despite his attempt to rehab his elbow, Osuna underwent Tommy John surgery in late June. On July 26, he was ranked 58th on MLB's revised Top 100 Prospects list, and the number two prospect in the Blue Jays organization.

Osuna made his first rehab appearance since the procedure on July 8, 2014, and pitched one inning for the Gulf Coast League Blue Jays. He was then promoted to the High-A Dunedin Blue Jays and made seven starts before the end of the season, posting a 0–2 record, a 6.55 ERA, and 30 strikeouts in 22 innings pitched. In the 2015 preseason prospect rankings, he was named the number six prospect in the Blue Jays organization by MLB.

Osuna was invited to spring training in 2015 as a non-roster invitee. While initially not expecting to have any chance at making the major league team out of camp, Osuna impressed Blue Jays management through the first half of the spring. On March 22, he started a game against the Tampa Bay Rays and pitched 3⁄3 scoreless innings. After Steve Delabar was optioned to minor league camp on March 26, it was reported that Osuna would likely make the Opening Day roster as a reliever. His position on the roster was confirmed on March 31.

Osuna made his Major League debut in a game against the New York Yankees on April 8, 2015, striking out Alex Rodriguez and getting Stephen Drew to flyout. In making his debut, Osuna became the youngest pitcher to appear in a Major League game for Toronto, at 20 years and 60 days old. Through the first month of the season, Osuna became the most reliable arm in the bullpen for the Blue Jays, posting a 1.38 ERA through his first 10 appearances. He earned his first win on May 18, pitching 1⁄3 scoreless innings in a 10–6 victory over the Los Angeles Angels of Anaheim. In doing so, Osuna became the youngest pitcher to earn a win for the Blue Jays, at 20 years and 100 days old. He earned his first career save on June 22, closing out an 8–5 win over the Tampa Bay Rays. On August 7, Osuna became the youngest player in MLB history to record an extra-innings save, when he closed out a 2–1 win over the New York Yankees in the tenth inning. Osuna finished the 2015 regular season with a 1–6 record, 20 saves, 2.58 ERA, and 75 strikeouts in 69⁄3 innings pitched, and was the youngest player in the AL.

In the 2015 American League Division Series, Osuna recorded a five-out save in the fifth and final game, and in doing so became the youngest pitcher in American League history to record a save in the postseason, as well as the second-youngest to do so in MLB history, behind Don Gullett in 1970. Osuna pitched in 4 of the 5 ALDS games, and did not allow a baserunner in 5⁄3 innings pitched. He finished fourth in American League Rookie of the Year, receiving two second-place votes and two third-place votes.

On December 5, 2016, Osuna committed to play for Team Mexico at the 2017 World Baseball Classic.

On July 30, 2018, the Blue Jays traded Osuna to the Houston Astros for pitchers Ken Giles, Héctor Pérez, and David Paulino. The Astros reinstated him to their active roster on August 5. He was loudly booed in his first appearance in Toronto as a member of the Astros. In 2018, between the two teams he was 2-2 with 21 saves and a 2.37 ERA.

On May 8, 2018, Osuna was arrested by Toronto police and charged with assault. He allegedly assaulted Alejandra Roman Cota, the mother of his 3-year-old son. Roman Cota was visiting Toronto with their child. She returned to Mexico shortly afterward and refused to return to Toronto. Due to Roman Cota's refusal to testify, the prosecution withdrew the charge against Osuna in exchange for a peace bond, mandating that for one year he not have contact with the alleged victim. He was placed on administrative leave by MLB commissioner Rob Manfred.

On June 22, 2018, he received a 75-game suspension without pay for violating the league's domestic violence policy, retroactive to May 8.

In 2019, Osuna led the American League with 38 saves and 56 games finished. He also recorded a 2.63 ERA and 73 strikeouts in 65 innings. His 154 career saves at season's end were 10th-most among all active pitchers.. On October 29, 2020, Osuna was placed on outright waivers by the Astros and became a free agent.