On January 17, 1997, he lost to John Lober in Hawaii's Superbrawl by split decision. Despite dominating the first three minutes of the fight, including a leglock which broke Lober's ankle and some strikes which blew out his front teeth, Shamrock's lack of cardio became a factor, and Lober was able to come back and punish him until winning the decision. After his loss, Shamrock shifted the focus of his career exclusively to mixed martial arts. Shamrock then fought top ranked Japanese fighter Tsuyoshi Kohsaka in RINGS and defeated Kohsaka by decision.