Formerly a starting quarterback for the Auburn football team, Gross was drafted by the Toronto Blue Jays in the first round (15th overall) of the 2001 amateur entry draft. Promoted from Triple-A Syracuse on August 7, 2004, he saw limited duty against left-handed pitching.
Gross has excellent power, and though he is a big man, possesses good speed. In September 2004, he belted his first major league home run off the Oakland A's Justin Duchscherer. His outfield range is very good, and he has a strong arm. In 38 games, he collected 73 putouts with five assists and one double play in 78 total chances, for a perfect 1.000 fielding percentage.
On December 7, 2005, Gross was traded by the Blue Jays to the Milwaukee Brewers, along with pitchers Dave Bush and Zach Jackson, in exchange for first baseman Lyle Overbay and pitching prospect Ty Taubenheim.
At the beginning of the 2006 season with the Brewers, he obtained the nickname "the Southern Gentleman" for his politeness and well-mannered attitude both on and off the field.
The plan was to have him share time with Tony Gwynn, Jr. and Gabe Kapler in center field in 2008. With a focus on defense, Yost indicated in March that Gwynn and Kapler might have a leg up on Gross.