Being a tough bar room brawler doesn't mean a whole lot in the UFC ring. All it means is that basically, if you're lucky enough, one of the three punches that you attempt every round might land, before you're taken down which you have absolutely no technical knowledge whatsoever and get beaten up, gassed out or submitted.
And if you are a 350 pound behemoth, you'll be huffing and puffing in 2 minutes after the first takedown. No chance.
I would have thought this would have been obvious watching yet another borefest where that exact thing happens with GSP lying onto of a guy after 30 secs of ever round.
I'm sure there are some great brawler boxers that never did anything with it, though. Just saying, it's pretty damn obvious what would happen in a ufc fight in that scenario.