Previously, Clark has played with the Detroit Tigers (-), Boston Red Sox New York Mets New York Yankees Arizona Diamondbacks (-), San Diego Padres and again with the Diamondbacks starting in July, 2008. He is a switch hitter and throws right-handed.
Clark was selected an All-Star in 2001.
On June 29, 2004, at Yankee Stadium, Clark hit a deep center field two-run homer off Derek Lowe, to help his team to an 11-3 win over the Red Sox. Clark joined Bernie Williams and Danny Tartabull as the only players to reach the center field bleachers more than once since the remodeled Yankee Stadium opened in .
Clark signed with the Arizona Diamondbacks after the 2004 season. In 2005, he enjoyed monstrous success with the D-Backs. In a limited role (349 at-bats), he hit .307, belted 30 home runs and knocked in 87 runs. In , Clark was injured for a vast majority of the season, which rendered him ineffective.
In 2007, Clark shared the first baseman position with Conor Jackson. He played in 113 games, and batted .249. Though not with the best batting average, Clark would go on to lead the Diamondbacks into the playoffs. He led the young team with the slogan "Anybody, Anytime" which he came up with to describe the Arizona team. After the season, his contract was up and he did not re-sign with the Diamondbacks.
On February 10, 2008, The San Diego Union-Tribune reported that Clark agreed to a one-year contract worth $900,000 with the San Diego Padres. On June 8, 2008, Clark hit a game-winning three-run pinch-hit home run off Mets closer Billy Wagner in the eighth inning to give the Padres an 8-6 win over the Mets at PETCO Park.
Clark has filled in a variety of capacities with the Major League Baseball Players' Association, serving as the club player representative for the Boston Red Sox in 2002 and Arizona Diamondbacks as recently as 2006. Clark, along with Mark Loretta, was re-elected as Associate Player Representative on the MLBPA Executive Board upon the ratification of the new collective bargaining agreement on December 8, 2006.