Of all the opponents Nick Diaz has faced in his career—many of whom are world class fighters—I think we always knew that the hardest obstacle for Nick Diaz to overcome would be Nick Diaz.
The story of Nick's MMA career reads like a recurring, cyclical narrative about great potential cut down by bad personal choices.
And Diaz? Well to me, a fight with BJ Penn is a form of punishment in and of itself, since "The Prodigy" represents a horrible stylistic matchup for him.
Is it a worse matchup then GSP would have been? That's debatable, however there are a couple factors that potentially make this fight more dangerous for Diaz. Against the Canadian, Diaz knew he had only one thing to fear, expect, and prepare for: the takedown. Sure, it may have proven his downfall, but at least he knew what to train for and (hopefully) defend against with his BJJ.
GSP's standup might have been effective, but it would only have set up the takedown. Against Penn, Diaz has to worry about a fast opponent with great technical boxing and proven one-hit KO power. As a high-volume puncher, he also has to worry about Penn's legendary chin and un-cut-able skin, Finally, Penn has the sort of killer instinct that some of Diaz's past opponents (and possibly even GSP) lack.
Put another way: if Diaz had flopped to the canvas like he did against Paul Daley against BJ Penn instead, the fight would have ended a minute later with Penn licking Diaz's blood off his gloves.
So to all you angry fans out there: relax. No one has any right to be angry here. Not Diaz, who's lucky he still has a place on this card at all. Not Penn, who traded one exciting, winnable fight for another. Not the UFC, which gets to keep it's blockbuster October event (mostly) intact. And not the fans, who will be treated to a great fight and a (supposedly) routine GSP title defense, just like they were before all this went down.
In fact, the only person with a legitimate gripe is St. Pierre himself, who took time off training, dusted off the old pinstripe suit, and got his “best GSP you've ever seen” stock answers ready only to be rewarded with frustration, and 11th hour change of opponent, and the loss of his head coach. Talk about a burr in your saddle.