The former UFC champion made his Pride FC debut in 1999 at Pride 6 against the popular Akira Shoji. The two fighters passed most of the first round in the clinch, where Mezger landed strikes and tried unsuccessfully to take down Shoji. At the second, Akira scored a takedown and performed ground and pound, which Mezger retaliated by controlling the striking again when they returned to their feet; however, the Japanese took Mezger's back on the ground towards the end of the round and scored punches while Guy attempted to escape. At the third and final round, the two traded strikes again and Shoji repeated his back siege before the fight ended. The judges decreed a split decision and it was given to Shoji.