Bradley's lost steam in the final 6 rounds. Swollen eye or Fatigue?

I had the fight 8-4 Bradley. It was a bad decision. The headbutt in round 2 changed the fight slowly. In about round 5 or 6, the eye started to swell up probably after Chaves hit the eye couple of times. Bradley started to fight on the outside when he was clearly having success fighting in the phonebooth. With the bad eye, I could see why he'd stay away because he couldn't see all punches coming. And Chaves is obviously a dangerous puncher. Was it the eye or could it have been fatigue? He did admit he got fatigued in PAC-Bradley 2 the last 6 rounds and couldn't keep up. In this fight, Diaz kept saying stuff like "Tim, you're not tired, are you?"...etc.. So there could be a case here. I personally believe it was the eye, but in Bradley's future fights, we need to watch if there's a pattern here.