I give GSP the benefit of the doubt, he was off for 18 months and was rusty, so I thought it was a rarity when he got tired. But, in this fight, he seemed smaller than ever before it seems, nowhere near as big as before. And his striking defense is nowhere near where it was. Diaz I think did a nice job on the feet, especially in the 3rd round. But, if you can't neutralize his takedown D like Anderson, you aren't stopping GSP at 170. He seemed real tired during the middle of the 3rd round. It seems like he lost part of his explosiveness and speed, so injuries plus all the fights he has might be taking a toll on his body now. But, nobody at 170 is beating GSP.
Unless Demian Maia somehow acquires K-1 level striking and World Class boxing, nobody is beating GSP at 170.