Nate Cornejo was drafted in the first round of the 1998 MLB draft by the Detroit Tigers. He was the 34th player selected in the draft.[3] Following the draft, he made his professional debut as a member of the Gulf Coast League Tigers. Cornejo recorded a 1–0 record in 5 appearances, posting a 1.26 earned run average over 14.1 innings.[4]
For the 1999 season, Cornejo was promoted to the Single–A West Michigan Whitecaps of the Midwest League. He made 28 starts, posting a 9–11 record and a 3.71 ERA. In 174.2 innings, Cornejo struck out 125 batters and walked 67.[4]
Cornejo split the 2000 season between the Single–A Lakeland Tigers of the Florida State League and the Double–A Jacksonville Suns of the Southern League. In 12 starts for Lakeland, he compiled a 5–5 record and a 3.04 ERA, with 60 strikeouts and 31 walks over 77 innings. Cornejo started 16 games for Jacksonville, posting a 5–7 record and an earned run average of 4.61. In 91.2 innings for Jacksonville, he recorded 60 strikeouts and 43 walks.[4]
In 2002, Baseball America listed Cornejo as one of the top 100 prospects in baseball.[6]
In his lone full season with Detroit in 2003, Cornejo finished the season with a 6–17 record. He had the lowest strikeout rate of any starting pitcher in over 20 years, striking out just 46 batters in 194.2 innings.
Cornejo played for the Detroit Tigers until 2004 and was released to free agency in 2005. He was signed by the Chicago White Sox to a minor league contract in April 2006. Cornejo pitched four games in the minors before officially retiring on July 2, 2006.