The Orioles' Trey Mancini and the Giants' Buster Posey were named MLB's Comeback Players of the Year for 2021 on Monday. 

Mancini won the American League Comeback Player of the Year Award after beating colon cancer and returning to Baltimore to post the fourth 20-home run season of his career. Posey won the National League Comeback Award following one of his best seasons since winning the MVP Award in 2012, after he didn't play at all in 2020 due to COVID concerns.

• All-time MLB Comeback Player of the Year winners

Mancini missed all of the 2020 season as he underwent treatment for Stage 3 colon cancer, which he was diagnosed with in March of that year after a colonoscopy revealed a malignant tumor. He had surgery to remove the tumor and went through six months of chemotherapy, returning for Spring Training 2021 cancer-free. 

On Opening Day, Mancini knocked a single down the third-base line at Fenway Park for his first hit since returning to baseball. He hit his first home run on April 10 in Baltimore, and on June 20 at Camden Yards, he hit the 100th home run of his career. By the end of the season, the 29-year-old first baseman had played in 147 games, batting .255 with 21 homers, 71 RBIs and 77 runs scored. Mancini even competed in the Home Run Derby -- and nearly won it, before falling to Pete Alonso in the finals.

Posey elected not to play in 2020, and the Giants' longtime catcher returned to lead San Francisco to the best record in baseball in '21. Behind Posey's .304 batting average, 18 home runs, 56 RBIs and .889 OPS, the Giants set a franchise record with 107 wins. During the playoffs, Posey became the Giants' career postseason hits leader, with 57, and he's also played the most postseason games in franchise history, with 58.

It was a resurgent season even compared to the last one he played, 2019, when Posey batted a career-low .257 with only seven home runs and a .688 OPS. This year, Posey's home run total was his highest since 2015, and his OPS was his highest since 2012. Posey led all catchers with at least 100 games played in both batting average and OPS, and he was named the NL Silver Slugger at catcher for the fifth time and an All-Star for the seventh time.

At the end of his Comeback Player of the Year season, Posey announced his retirement, still at the top of his game. The 34-year-old played all 12 seasons of his career with the Giants and was a three-time World Series champion with the team. Posey is only the second player to retire after being named Comeback Player of the Year since MLB first presented the award in 2005, along with Yankees closer Mariano Rivera after the 2013 season.

Mancini is the first Oriole to win MLB's Comeback Player of the Year Award. Posey is now a two-time Comeback Player of the Year -- he also won the award in 2012 and is the only Giants player to win.

The MLB Comeback Player of the Year Award winners are determined by a vote from the 30 MLB.com club beat reporters. Last year's winners were Royals catcher Salvador Perez and Rockies closer Daniel Bard.