He played college football for the Tennessee Volunteers and was selected by the Packers in the second round of the 2000 NFL draft.

[3] Clifton's team lost in the state playoffs in his junior and senior years to Briarcrest Christian School in Memphis, Tennessee, whose offensive coordinator was former Ole Miss head coach Hugh Freeze.

[5] During these four years, the Tennessee Volunteers enjoyed great success with a 43–7 record and a win in the Fiesta Bowl over Florida State following the 1998 regular season to claim the National Championship.

[10] He enjoyed continued success during his second season when he established a reputation as one of the NFL's best and unheralded blindside blockers for Brett Favre.

[12] However, on November 24, he suffered a severe pelvic injury after receiving a blindside hit from the Tampa Bay Buccaneers defensive tackle Warren Sapp.

[13] Because the incident occurred after an interception with Clifton far from the play, Sapp received harsh criticism for his action.

[17][18][19] For his part, Sapp did not visit or telephone Clifton during his four-day stay in a Tampa Bay hospital.

[21][22] In 2005, the NFL Competition Committee agreed on new guidelines for "unnecessary roughness", making hits such as that suffered by Clifton illegal.

[33][34] He went to Hawaii to the Pro Bowl with teammates wide receiver Donald Driver, defensive end Aaron Kampman, and cornerback Al Harris, as well as head coach Mike McCarthy.