Some people might disagree with having this fight on the list because it was not Penn's most exciting bout, but I believe the significance of it is enough for it to be here.
BJ has made it known that he wants to earn another shot at the welterweight title.
That fight would be a tough sell because Penn was thoroughly dominated by the current UFC welterweight champion, Georges St-Pierre, last time the two met.
The reason GSP was able to handle BJ so easily was his superior wrestling.
In order to get a rematch with Georges, Penn needed to show that his grappling ability had improved significantly, and he showed that it had definitely improved when he fought Jon Fitch.
Penn managed to win the first round against Jon using his grappling ability, and he arguably could have been given the second round as well.
The fight went to a draw, so Penn did not receive a title shot, but he did succeed in showing us how another fight with St-Pierre might go differently, and that's an important step towards getting another crack at the belt.