For whatever reason, sometimes I am only able to find one card of certain players. To be considered a One-Card Wonder, a player must have been active since 1991 (when I started paying attention).
This is a 1995 Pacific card of a little-used reliever. It is the only Boston Red Sox card out there of him. Valdez only pitched in 12 games for Boston in 1994, but he got a card thanks to Pacific's commitment to Latin players. He pitched to the tune of an 8.16 ERA with four strikeouts compared to eight walks. It's no wonder he did not last long.