Trey Mancini

On March 7, Mancini left the Orioles during spring training to undergo a non-baseball medical procedure. On March 12, it was revealed that the procedure was the removal of a malignant tumor from his colon. On April 28, Mancini revealed he had stage 3 colon cancer and will begin chemotherapy ongoing for six months to treat his cancer. Mancini said if baseball resumed in 2020, it would probably be without him.

Mancini got off to a strong start in 2019 and was leading the Orioles in most offensive categories in late-April. He is one of three MLB players along with Alex Bregman and Anthony Rendon with at least 35 doubles, 34 home runs and 100 runs in 2019. He set a career high with five hits in an 11–4 win over the Toronto Blue Jays at Rogers Centre on September 24, 2019. He ended the season hitting .291 with 35 home runs and 97 RBI.

Mancini batted leadoff for 51 of 156 games played in 2018. He ended the season hitting .242 with 24 home runs and 58 RBI.

Mancini made the Orioles' 2017 Opening Day roster after transitioning to the outfield. On April 16, Mancini recorded his second multi-home run game of the season, while driving in four runs. He tied Trevor Story and Dino Restelli for most home runs through a players first 12 career games with seven. On April 22, Mancini hit his fifth home run of the season and eighth of his career. He tied Story and Carlos Delgado for most home runs through a player's first 17 career games.

After spending some time in Baltimore during spring training, Mancini returned to Bowie to start the 2016 season. He was blocked at Triple A by Joey Terdoslavich, but was promoted to the Triple-A Norfolk Tides in April 2016 as Terdoslavich struggled. He spent the remainder of the season at Norfolk, batting .280 with 13 home runs and 54 RBIs in 125 games.

The Orioles promoted Mancini to the major leagues on September 18, 2016 during September call-ups. On September 20, in his major league debut as the designated hitter against the Boston Red Sox, he hit a home run against Eduardo Rodríguez in his second at bat, making Mancini the fourth Orioles' player to hit a home run for their first Major League hit after Larry Haney (1966) Nick Markakis (2006) and Jonathan Schoop (2013). Mancini started again two nights later and hit his second career home run, a three-run homer off David Price. He became the 20th player in Major League history to hit a home run in his first two starts. He would then become the third player in Major League history to homer in their first three starts, after he hit a solo home run against the Arizona Diamondbacks on September 24.

The Orioles selected Mancini in the eighth round of the 2013 MLB draft. He signed, and made his professional debut with the Aberdeen IronBirds of the Class A-Short Season New York–Penn League that same year. He spent the whole season with Aberdeen, batting .328 with three home runs and 35 RBIs in 68 games. He began the 2014 season with the Delmarva Shorebirds of the Class A South Atlantic League and received a midseason promotion to the Frederick Keys of the Class A-Advanced Carolina League. In 137 games between the two teams, he compiled a .284 batting average with ten home runs and 83 RBIs. He began the 2015 season with Frederick, and was promoted during the season to the Bowie Baysox of the Class AA Eastern League. In 136 games, Mancini slashed .341/.375/.563 with 21 home runs, 89 RBIs, and 43 doubles.

Mancini attended Winter Haven High School in Winter Haven, Florida, where he batted .480 with six home runs as a senior. After high school, he attended the University of Notre Dame where he played college baseball for the Notre Dame Fighting Irish and pursued a degree in political science. He played collegiate summer baseball for the Holyoke Blue Sox of the New England Collegiate Baseball League in 2011, and the Harwich Mariners of the Cape Cod Baseball League in 2012. In 2013, his junior year at Notre Dame, he slashed .389/.431/.603 with seven home runs and 54 RBIs in 57 games.

Joseph Anthony "Trey" Mancini III (born March 18, 1992) is an American professional baseball first baseman and outfielder for the Baltimore Orioles of Major League Baseball (MLB). He made his MLB debut in 2016. His nickname Boomer, originally "Boom Boom" after Ray Mancini, had morphed into its current form when he matriculated at the University of Notre Dame.

On June 7, in a game against the Pirates, Mancini hit a game-tying, pinch-hit two-run home run in the ninth inning off closer Tony Watson. Two innings later, with two on and two outs, Mancini hit a walk-off three-run home run off Wade LeBlanc to give the Orioles a 9-6 victory. Per STATS LLC, Mancini became the first Oriole to hit a pinch-hit homer in the 9th inning or later and then hit another home run in the same game. He also became the second Oriole ever to hit a game-tying home run in the 9th inning or later and then hit a walk-off homer in the same game (Mike Young on May 28, 1987). He also joined Boog Powell ('66) and Eddie Murray ('80) as the only three Orioles to homer in the 9th inning and in extras in the same game.

On June 25, Mancini hit his 14th home run of the year, giving him the most home runs before an All-Star break by an Orioles rookie.