Bob Hamelin
Here it is - the worst baseball card of all time according to an article on Slate Magazine. It just so happens that the subject of the card, Bob Hamelin, played for the 1987 Cape League champion Harwich Mariners. Other members of that championship squad were six other Major Leaguers, including Gary DiSarcina (now Manager of the Pawtucket Red Sox) and John Flaherty (who started his career with the Red Sox).
Hamelin earned 1994 AL Rookie of the Year honors with 24 home runs and 65 RBIs. His power at the plate earned him the nickname "The Hammer". After a six year Major League career, he retired abruptly in 1999 from the AAA Toledo Mud Hens after grounding out and telling his manager that he was done. Bob Hamelin is currently a scout for the Boston Red Sox.
Related: I found a May 31, 1986 article online from the Los Angeles Times announcing that Hamelin will play baseball for UCLA instead of pursuing a football scholarship at Notre Dame. The LA Times actually has a full archive of many articles about Hamelin.