In his Major League Baseball (MLB) career, he played for the Pittsburgh Pirates, Texas Rangers, St. Louis Cardinals, Colorado Rockies, Chicago White Sox, Kansas City Royals, Washington Nationals, Cincinnati Reds, and San Diego Padres between 1999 and 2012.

Wells attended Elkins High School in Missouri City, Texas, and played for the baseball team and was an honor roll student.

In his debut against the Detroit Tigers, Wells went 5.1 innings, giving up 6 hits, 2 runs and 1 earned run while walking 2 and striking out 4 for his first Major League victory[3] After the 2001 season, in which he split time between the starting rotation and the bullpen, Wells was traded to the Pittsburgh Pirates.

He made a promising start against the Florida Marlins on July 18, when he threw eight shutout innings in a 6-0 Cardinals win.

[7] Wells began the 2008 season compiling a 2.29 ERA in ten games with 16 strikeouts as the primary long relief pitcher out of the bullpen.

[9] He was brought up to the majors to pitch out of the bullpen, but was ineffective, posting a 6.49 ERA in 26+1⁄3 innings before being placed on the disabled list with a right adductor strain on June 2.

On July 9, 2009, Wells signed a minor league contract with the Cincinnati Reds, and was assigned to their Triple-A affiliate, the Louisville Bats.

On February 13, 2010, the Cincinnati Reds re-signed Wells to a minor league contract that included an invitation to spring training.

On July 14, 2010, Wells signed with the Long Island Ducks of the Atlantic League of Professional Baseball.

[21] In 2016, Wells was named the pitching coach for the Rancho Cucamonga Quakes, the Los Angeles Dodgers' Single-A affiliate in the California League.