As a member of the Boston Red Sox in the 2005 season, Clement was named as an All-Star Game selection for the first time in his big league career, replacing injured Blue Jays pitcher Roy Halladay.

On July 26, 2005, Clement was struck in the head [1] by a line drive from Carl Crawford of the Tampa Bay Devil Rays.

He was rehabilitated at the Red Sox extended spring training complex in Fort Myers, Florida, but did not make a major league appearance in the 2007 season.

The Cardinals cited his recent rehabilitation and physical as reasons for adding him to the starting rotation for the 2008 season with no expected limitations upon reporting to Jupiter, Florida for spring training.

On June 3, Clement made a minor-league rehab start at Single-A Palm Beach, allowing only 1 hit over six innings.