Nick Diaz started slowly against BJ Penn in the main event of UFC 137, but as the fight progressed he began to look every inch the next welterweight title contender as he laid siege to the Hawaiian legend and emerged with a well earned decision victory.

Right from the opening bell the two fighters were engaging in the stand-up battle. Penn appeared to be getting the better of it with his head movement being key, allowing him to slip and then rip in with punches of his own.

Interestingly Diaz briefly tried to press Penn up against the cage, and when they broke free Penn executed the first takedown of the night and after a brief scramble attempted to take Diaz back, though he couldn’t quite get it though he did land a few short blows to the head.

Before long Diaz had worked his way back to his feet and Penn again began to go back to working well in the striking department, and his ability to dodge his opponents strikes appears to have reduced Diaz normally much more active offensive output.

Onto round two and Diaz, who was already showing signs of wear and tear on his face, wasted no time in turning the screw.

After shrugging off an early takedown attempt from the Hawaiian he began backing Penn up against the fence and then started to unload with some of his trademark accurate striking combinations to the body and head of his opponent.

Penn didn’t appear too comfortable cornered like this and wasn’t having the same success dodging punches as he had earlier in the fight which only encouraged Diaz further as his own tempo increased.

The repeated blows take their toll and Penn is also now sporting blood on his face and looks to be running low on both energy and ideas, trying to circle away from Diaz, but not succeeding while only getting off ocassional offense of his own, and it’s not enough to back him up.

Onto the final round with Diaz now firmly in control and Penn’s right eye rapidly swelling shut. It’s clear from the off Penn would like to get another takedown, but he’s weary and doesn’t have the speed required to catch Diaz off-guard.

Meanwhile Diaz gets right back to his excellent combination work and is now dismantling Penn much as he has a number of other opponents over in Strikeforce in the past few years.

To his credit Penn is taking everything he’s giving him, and as the round progresses he starts to rediscover a little of the success that he had in the first round by pressing forward and using head movement to dodge strikes and then follow up with some of his own.

There’s two problems though. Firstly he’s too tired to land with full power, and secondly he’s only being effective when he’s moving forward – when Diaz does the same in reverse he quickly falters and finds himself back up against the cage being bombarded with strikes.

The fight continues in this fashion until the final bell with Diaz still clearly having the upper hand though he eats a number of strikes along the way.

And so it’s on to the judges scorecards and they all see it in Diaz favor (29-28 x2, 29-27).

Afterwards an animated Diaz calls out Georges St.Pierre and claims that the champion is faking an injury as he’s scared to fight.

Following on from that a dejected Penn states that he wants to retire as he isn’t performing as well as he would like and doesn’t want to go home to his daughters looking beaten up like this.