After a brief retirement, Shamrock returned to mixed martial arts as a career. He signed a deal to fight Brazilian Jiu-Jitsu standout Elvis Sinosic at K-1, the premiere kickboxing event in the world. Shamrock beat Sinosic via unanimous decision after five three-minute rounds. Later, when Sinosic faced Tito Ortiz for the UFC light-heavyweight title (formerly the middleweight title) at UFC 32, Shamrock served as guest commentator. On August 11, 2001, he took on his former student, Shannon Ritch in a kickboxing match for K-1. Just 56 seconds into the first round, Shamrock broke Ritch's arm with a roundhouse kick and thereby won the match.