Mitre was the Chicago Cubs 7th-round selection in the 2001 Major League Baseball Draft out of San Diego City College. He was the second player out of the 2001 draft to make it to the majors with the Cubs, the first being Mark Prior. Mitre made his major league debut for the Cubs in after being called up from the West Tenn Diamond Jaxx (at the time, West Tenn was the Cubs' Double-A affiliate). He played in 3 games in 2003 (2 starts) and had an 0–1 record with an 8.31 ERA.