He played Major League Baseball (MLB) for the Colorado Rockies, Oakland Athletics, San Diego Padres, Seattle Mariners and Baltimore Orioles.

[3] Smith made his MLB debut with the Colorado Rockies on September 16, 2007,[4] in a 13–0 home win over the Florida Marlins.

Smith's successful stint during the regular season earned him a spot on the Rockies' 2007 postseason roster.

The next batter, Colorado second baseman Kazuo Matsui, went on to hit a memorable grand slam to give the Rockies a lead that they would never relinquish.

This time, Smith hit a double that came with two outs and two runners in scoring position in the bottom of the fourth inning with the Rockies down, 1–0.

Smith also hit his first career inside the park home run that season, which was the eighth in Colorado Rockies history.

[9] On March 30, 2014, Smith hit a home run against Los Angeles Dodgers pitcher Brian Wilson in his first at-bat as a Padre.

On December 30, 2014, the Padres traded Smith to the Seattle Mariners in exchange for pitcher Brandon Maurer.