Mezger faced two time ADCC champion Ricardo Arona at Pride 16. Mezger entered the ring with an American flag draped across his shoulders out of respect for the World Trade Center attacks in New York. He also wore trunks with an American flag design. Arona and Mezger circled each other for a few moments, before moving in and exchanging strikes. Mezger ended the round one with two takedowns and side mount position but couldn't capitalize on it. The second round was much of the same until Mezger landed a stunning kick to Arona's face. The third round took a different turn with three minutes left in the round, Arona scored his only takedown of the fight. The third round continued like this, with Arona laying on Mezger, using his ground and pound style for the last three minutes of the bout. Although Mezger controlled the first two rounds (1st round being 10 minutes and the second and third rounds were 5 minutes each), the judges awarded a controversial split decision victory to Arona, causing many to feel that Mezger was robbed of the win.