Well, in the Adrenaline MMA III: Bragging Rights event hosted in Arizona back in 2009 we got the answer to the long-debated question. Who would win between a heavyweight boxing champion and an MMA heavyweight champion?In the footage, we get confirmation of what's long been said, through the triumph of former heavyweight boxer Ray Mercer over his opponent, MMA heavyweight Tim Sylvia.In what was originally supposed to be a boxing match, The then 48-year-old Mercer knocked out Sylvia in under 10 seconds with a heavy right hand, knocking him out. Due to regulation troubles, the match was turned into an MMA fight however it didn't seem to make Ray any less comfortable. Mercer had just one MMA fight prior to this event when he competed against Kevin 'Kimbo Slice' Ferguson in 2007. Despite this Ray had the utmost confidence and stated: I'm not going to be kicking, I’m going to wear shoes and all that. I want him to know straight up where I’m coming from. I am a boxer, I’m not an MMA fighter.After a poorly executed kick by Tim Sylvia, Ray Mercer seems to almost take a moment to calculate the exact power and trajectory needed to knock his opponent to the ground, and he then executes it flawlessly. Check out the footage that puts boxers on top of the fighting world in the video above.