Albert Pujols
After one full season with the Chiefs, Pujols got onto the Cardinals' roster after a teammate got injured.  Later two of the Cardinals' best players also got injured, and Pujols became a regular player.  In his first season with the Cardinals, he had 37 RBIs and 130 home runs, and posted a .329 on-base average.  He won the Rookie of the Year Award, earning every vote.