He's is probably the first person to come to mind when the topic of disabled professional athletes is breached. Abbott played baseball successfully with only one hand (he was born without his right hand). He attended the University of Michigan and was drafted by the California Angels in 1988 with the 8th overall pick. The Angels then allowed him to start the 1989 season as a member of their starting rotation without having played a single minor league game. Surprisingly he won 12 games and had an ERA under 4.00. He threw a fastball, cut fastball, slider and sometimes a curveball. Abbott's biggest accomplishment came on September 4th, 1993 when as a New York Yankee he no-hit the Cleveland Indians. Abbott formally retired in 1996 and returned to the MLB in 1998 to moderate success before retiring entirely in 1999 as a member of the Milwaukee Brewers. Some of his career totals: 1674 innings, 31 complete games, 888 strikeouts.
Maybe Antonio's specific physical condition isn't grounds for the label 'adversity' or 'disability' but having six fingers on each hand is certainly worth a mention in this article. His condition is known broadly as polydactyly and has resulted in him being born with six fingers on each hand and six toes on each foot. His grandfather has the same condition. Most agree that having these extra digits did not help Alfonseca in any way since he did not use the fingers when he pitched (they didn't touch the ball). His career numbers would support that notion. He still plays pro ball with the Bridgeport Bluefish of the Atlantic League.
Pete Gray was a one-armed outfielder who played for the St. Louis Browns at the major league level. He also played for a number of different 'minor league' teams. 1945 with the Browns was his only season playing Major League ball and he produced modestly in 77 games: .218 batting average and more walks than strikeouts. Also surprisingly, Gray was not a liability in the field where he had learned how to transition the ball from his glove to his hand fairly quickly.
Players Suffering from Social Anxiety Disorder
While the effects of social anxiety disorders are not explicitly physical players who are subject to this condition often find it difficult to perform up to their abilities.
Probably the most well-known case of a player with diagnosed social anxiety disorder is Cy Young winner Zack Greinke. In 2004 Greinke debuted at the major league level with the Kansas City Royals where he pitched 145 innings in 24 games, ending with a 3.97 ERA. His 2005 season wasn't as good (183 innings, 1.56 WHIP, 5.80 ERA) but for a 23 year old with 24 games of ML experience it was considered developmentally appropriate. In 2006 Greinke left Spring Training for reasons associated with his social anxiety disorder and depression. He was eventually put on the 60-day DL and took a break from baseball. During 2006 he returned to AA Wichita and later to the Kansas City Royals for a few relief appearances. Since the 2007 season Greinke has pitched like an ace at the major league level. He was traded to the Brewers before the 2011 season and has won 7 out of 11 games for them so far in the 2011 season. Other major league players have suffered from social anxiety disorder or depression include Joey Votto and Khalil Greene.