In 2002, Lehman moved to weakside linebacker, replacing Butkus Award winner Rocky Calmus. Lehman was recognized as a consensus first-team All-American, after receiving first-team honors from the Associated Press, the Football Writers Association of America, the Walter Camp Foundation, "The Sporting News", CNNSI, ESPN and "Sports Illustrated". He posted six tackles (five unassisted) in the Rose Bowl against Washington State and sacked quarterback Jason Gesser twice for a loss of 17 yards. Both sacks ended scoring drives at the end of the second quarter and were instrumental in securing Oklahoma's first-ever Rose Bowl win.