He signed with the St. Louis Cardinals in 2002, and spent the season with their Eastern League double A affiliate, the New Haven Ravens.

At the end of the season, he became a rule 55 free agent, and signed with the Pittsburgh Pirates, and spent 2003 with the Altoona Curve, also in the Eastern League.

His .304 batting average, eight home runs and 58 runs batted in in 2005 was good enough for a September call-up,[4] and he made his major league debut on September 10, 2005, replacing Mike Redmond in the eighth inning of a 7–5 loss to the Cleveland Indians at Jacobs Field.

During the 2009 season, Heintz began coaching with the Twins' Midwest League affiliate, the Beloit Snappers.

[6] At the start of the 2010 season, the South Florida Bulls baseball team hired Heintz as an assistant coach.