He played in Major League Baseball (MLB) for the Pittsburgh Pirates, Atlanta Braves, Baltimore Orioles, Texas Rangers, Washington Nationals, and Milwaukee Brewers.

First, on July 22, 2003, where he was traded by the Pittsburgh Pirates with Scott Sauerbeck to the Boston Red Sox for Brandon Lyon and Anastacio Martinez.

Second, on July 31, 2003, where he was traded back to Pittsburgh with Freddy Sanchez and cash for Brandon Lyon, Anastacio Martinez and Jeff Suppan.

After experiencing a drop in velocity on his fastball in excess of 10 mph (16 km/h) in a game versus the Washington Nationals, the Braves quickly took precautionary measures and placed him on the disabled list on May 16, 2007, with a left elbow strain.

Gonzalez made his return on June 18, 2008, pitching a perfect 9th inning and recording a save against the Texas Rangers.