Fielder earned his first call-up to Major League Baseball on June 13, 2005. He served as the designated hitter for the Brewers during interleague play. With Lyle Overbay serving as the Brewers' regular first baseman, Fielder was sent back down to the Sounds after the end of interleague play. Fielder was again called up to the Majors on August 17, 2005, and went on to finish the season with the Brewers, where he was used as a pinch-hitter. He was the 6th-youngest player in the league.