This fight was actually closer in retrospect than I remembered it being. BJ absolutely lit Sherk up with the jab, but Sherk had his moments with the leg kicks and decent left hands. Ultimately, Sherk didn't try for more take downs because it was blatantly apparent after his first attempt that he wasn't going to be able to pull his traditional blast double or single leg take downs on a guy with legs made of rubber and it would just be a waste of energy to go that route. Also, a common side effect of spamming take downs on BJ involves him taking you down, followed by a RNC. I kinda wish he'd tried to force a more grappling-centric approach to test Penn's cardio here, but this version of BJ had deadly cardio to go with the best skills in the LW division.
In any event, I thought the stoppage was bullshit at the time and would have liked to see Sherk get a minute to recover from that near-death experience instead of having BJ call it for Yamasaki at the end of the round, but that just wasn't The Muscle Shark's night and it probably saved him from a way worse ass-whooping in the championship rounds. Still, that would have been an amazing comeback...
