Clark has previously played for the Oakland Raiders, Houston Texans, New York Giants, and New Orleans Saints.

He started 44 of 45 games played in 4 seasons was named honorable mention All-Big Ten three times as a linebacker, and finished his college career with the sixth most (384) tackles at Illinois, finishing just ahead of Pro Football Hall of Fame linebacker Dick Butkus.

As a senior in 1999, was named honorable mention All-Big Ten after started all 12 games and recorded a career-high 122 tackles, 3 sacks and an interception.

In the 2002 NFL season, he started all 16 games for them and finished as the Jaguars’ 2nd-leading tackler with a career-high 152 tackles, 2 sacks, 1 interception, a pass defensed and a forced fumble.

In 2005, he started 15 of 16 games for Oakland and led the Raiders in tackles for the 2nd consecutive season with 113 stops (82 solo), a sack and 7 passes defensed.

Clark signed a one-year contract with the Houston Texans on March 7, 2007, and he went on to appear in 13 games including eight starts, and recorded 51 tackles and an interception and a forced fumble.