In 2003, Martínez played for the Triple-A Buffalo Bisons and the Indians. He finished with a combined .315 batting average, hitting at a .349 clip in August and September with the big league club. Exhibiting knowledge of the strike zone and an ability to make contact, he reduced his strikeout totals and produced a combined .376 on-base percentage. He also drove in 63 runs, hitting .323 with runners in scoring position, and was selected to participate in the All-Star Futures Game played at Chicago's U.S. Cellular Field. From 2001 to 2003, the Venezuelan slugger batted a combined .330 with 40 home runs and 194 RBI.