Diaz was probably the worst guy in the division for GSP to look good against. Actually, while he was a good choice from a promotional perspective in terms of drawing hype, antagonizing GSP, and be an "interesting" personality, he was a terrible stylistic choice for the following reasons (ignore the fact that he was coming off a loss and a drug suspension):
1) He's got a god-like chin and is extremely durable.
2) He's got insane cardio
3) He's really good at defending himself on the ground
4) He's a fantastic grappler
5) Despite the above, his takedown defense was always pretty below-par
6) His main offense consists of cutting off the cage, pressuring, and volume punching
7) He lacks real one shot KO power and instead has to rely on overwhelming his opponent with combinations and body shots.
8) He's defensively iffy on the feet, and pretty hittable.
What the above meant was that St-Pierre, given his lack of serious KO power was never going to hurt Diaz on the feet, and wouldn't be able to get much going on the ground either. Meaning that not only did St-Pierre not have a real chance of finishing Diaz, he wouldn't be able to produce any damaging offense besides his jab.
Conversely, Diaz, despite being all but guaranteed to go the distance, had almost zero chance of actually winning the fight, or even produce any sort of offense whatsover. Playing an active guard game against St-Pierre is always a losing battle as his top game just stifles scrambles and submission attempts. Moreover, GSP is just way too technical/smart for him on the feet to just stand there, get closed down and eat combinations. He was always going to jab/circle, or switch levels and shoot for a double whenever Diaz committed.
In the end, you had a super tough guy who was never going to get finished or endure a serious beatdown, but with no real chance to win the fight either. Not a good combination.
With that said, I thought St-Pierre got more tired than usual. His takedowns in the final rounds of the fight lacked spring and explosiveness, and at times, they were a bit sloppy. Not sure if it was simply a flat performance, him having an off night, or his knee surgery slowing him down (it was hard to really judge after the Condit fight), but if I'm GSP, I'd alter my training methods a bit to regain his speed/explosiveness, which are huge aspects of his game. He looked a tad thicker around the shoulders, so maybe coming in a bit lighter against Hendricks would be wiser. I feel that as St-Pierre gets older and loses some of his athleticism, he needs to add some new tricks to his game to compensate.
