Nelson has played professionally for the Rookie Level Arizona League Brewers and Ogden Raptors, the Single-A Beloit Snappers and High Desert Mavericks, the Double-A Huntsville Stars, and the Triple-A Nashville Sounds.

For the 2008 season, he played with the Triple-A Nashville Sounds, but was called up to the Brewers on September 1; he made his major league debut that afternoon.

On September 2, Nelson collected his first major league hit, a pinch-hit double in the 10th inning against Luis Ayala of the New York Mets.

However, after going hitless in 21 at-bats primarily as a pinch hitter to start the season, Nelson was outrighted to AAA, and replaced with infielder Mat Gamel, on May 14.

After spending eight years in the Brewers organization, with 28 games at the major league level, Nelson signed a minor-league contract with the Seattle Mariners on May 19, 2009.