Mezger made his return to the ring at Pride 10 - Return of the Warriors, facing Brazilian superstar and future middleweight kingpin Wanderlei Silva. Mezger gained the upper hand early, cutting Silva with several crisp combinations and outpointing Silva on the feet. However, he was ultimately knocked out at the 3:45 mark. Shortly before the knockout, Silva was catching the worse end of the punching exchanges and proceeded to throw an intentional, illegal headbutt to Mezger that eventually led to landing the knockout combination. Many people felt as though this was a cheap shot that affected the end result. Some people, including Kazushi Sakuraba, felt the bout should have been changed to a no contest. Mezger talked about his feelings on the matter in an interview: "I am not going to cry foul, it is the fight game and things like that happen, get used to it. It is no win situation when it comes to answering that question, if I said it did (affect the result) then I would be making excuses. I would just like a rematch."