When it comes to the importance of victories, too much emphasis is placed upon weight class.
After defeating Matt Hughes, people acted as if Penn had just elevated himself to a new level.
Hughes was once a true pound-for-pound fighter, but last week he wasn't even a Top 10 welterweight.
More important than beating guys in multiple weight classes is being able to beat the very best in any one weight class, and at the present time, Matt Hughes isn't one of those guys. Georges St. Pierre and Frank Edgar are those guys.
That said, there are plenty of highly ranked fighters Penn could beat at welterweight, all the way up to heavyweight.
If he's motivated, Penn has a very good shot at beating Jon Fitch, the No. 2 welterweight in the world, and a P4P quality fighter. But victory against Fitch is far from certain.
Here are 10 fighters I'm far more convinced a motivated Penn would be likely to defeat...
Ben Askren is Bellator's welterweight champion and a great fighter. He's got legitimately world-class wrestling and enough of a top-game to stifle most of the fighters in the division.
But that wrestling wouldn't be nearly enough to stop Penn from submitting him once the fight reached the ground.
Of course, Askren could use his wrestling to keep the fight standing, but he doesn't have close to the level of striking necessary to hang with Penn on the feet.
Askren's only chance would be to somehow stall out a victory and hope that Penn tires himself out, but the odds would be pretty astronomical.
Less than a year ago, Paul Daley fought a title eliminator bout opposite Josh Koscheck.
Today, he's still ranked by many as a Top 10 welterweight.
A motivated Penn would beat him.
On the feet, Daley would have a serious advantage with his kicks, but he's probably not as good of a boxer as Penn, who could probably hold his own on the feet, if he was forced to do so.
The real area Penn would exploit Daley is on the ground, where Daley would be rendered nearly helpless.
If you're questioning whether Penn could take Daley down, consider that Jorge Masvidal, a blown-up and mid-level lightweight had a fair amount of success grappling with Daley.
Carlos Condit might actually be a tough test for Penn.
Penn doesn't like checking leg kicks, and Condit can mix some decent kicks into his arsenal to throw Penn off.
Condit also has a very good grappling game and is a decent wrestler.
Add on to that the fact that Condit's cardio is leagues above Penn's, and Condit looks like a serious threat to Penn.
Still, I don't think that Condit's wrestling is enough of a threat to put Penn on his back, and if he's forced to stand with Penn, there is a good chance Condit's wide-open stil leads to Condit taking a nap.
Nick Diaz has good boxing, good BJJ, a decent chin and great conditioning.
His only really big weakness is his takedown defense, which is the key factor in many of his losses.
That said, if he fought Penn, I don't think his takedown defense would be the problem. Penn is just a far better boxer than Diaz, has better BJJ and is far more explosive.
Diaz's only real chance against Penn would be to expose Penn's questionable endurance. Outside of that, I think Penn stuffs all of Diaz's takedown attempts and out-boxes him for as long as it takes.
Demian Maia is possibly the only fighter currently in the UFC with better submission grappling credentials than Penn.
A BJJ and ADCC world champion, Maia is capable of beating nearly anybody in the world in submission grappling, including Penn.
Unfortunately for Maia, he's not going to win many fights if he can't take them to the ground.
Penn's renowned takedown defense would probably be enough to keep the fight standing for long stretches, where Penn would have a big advantage.
If the fight was a trash-talking competition, I'd favor Sonnen by a large margin.
In an MMA fight, things would be different.
Sonnen is too slow to really beat Penn on the feet, and his eight submission losses make it hard to imagine that Sonnen would be able to stay out of trouble on the ground long enough to earn a decision.
Stefan Struve may be Dutch, but he's not a striker, he's a grappler.
Against Penn, one might imagine that his 60 or so pound weight advantage might be too much for Penn to overcome.
I don't think so.
Struve has abysmal takedown defense, which would likely be his undoing against Penn, who would proceed by slicing through Struve's guard and mauling him from the mount posititon.
Much like Carlos Condit, Kampmann brings a solid and well-rounded arsenal including good grappling and a diversified arsenal of strikes.
Also like Condit, Kampmann's chin is a bit too hittable for an elite fighter.
Heck, even Jacob Volkmann hit Kampmann solidly on the chin.
If Kampmann fought the smartest fight of his life, he might be able to keep Penn at bay with leg kicks.
The more likely scenerio involves Penn catching Kampmann on the chin with something heavy.
Gegard Mousasi, aka Fedor Jr., has a tendency to pull off wins from the brink of disaster.
Denis Kang had Mousasi in trouble on the feet and on the ground, before Kang's flakiness reared it's ugly head and he put himself into a triangle.
Against less-flaky opposition, Mousasi hasn't been so lucky. Akihiro Gono dominated Mousasi on the ground, eventually winning by armbar.
On the feet, Mousasi could hurt Penn, but as long as Penn didn't eat too many leg kicks, he'd probably wind up exposing the holes in Mousasi's defensive grappling.en route to a submission victory.
Much like Maia, Shields is one of the few guys in the UFC who could hang with Penn in a submission grappling contest.
But while Maia struggles when he can't get a takedown, Shields looks as if he might die at any second.
Even worse for Shields, he's about the only guy at 170 who wouldn't have a big conditioning advantage over Penn.
Shields may be one of the best fighters in the world in two weight classes, but Penn is an absolutely terrible stylistic matchup for him.
Perhaps even worse than GSP.
My conclusion on the next page.
Despite this list of highly ranked guys at higher weight classes, I'm still baffled by how much importance people place in the idea of being able to win in multiple weight classes.
My personal view is that it's far greater to be able to take on all comers within a single weight class.
I have no doubt that pound-for-pound quality fighters like Georges St. Pierre, Anderson Silva, Frank Edgar and Jose Aldo could have some real success against top-level fighters outside of their chosen weight classes.
Being great in two weight classes is obviously a remarkable achievement, but it's still not as great as being the very best in one.