Former UFC champion BJ Penn explained his decision to make a comeback during an appearance on the Just Scrap Radio show with Jens Pulver.

Penn, who retired following a loss to Nick Diaz last year, accepted Rory MacDonald’s recent challenge. The two will square off at UFC 152 in Toronto, Ontario, Canada on September 22.

“I got a lot of offers from all these other guys to fight, but when I got the offer from Rory, I said, ‘Good, I get to fight that brain of Tri-Star Gym,'” Penn said. “A lot of it is (trainer) Firas (Zihabi). They got a good thing going on up there, they have a good team, and they’re making a lot of waves. Of course, they got (Georges) St-Pierre, who is going to go down as the greatest welterweight in history, and now they got another guy they think will be the champion.”

MacDonald and GSP are close training partners up in Canada at the gym. Many have pegged MacDonald as the future of the division, or whichever division he ends up in.

Penn’s loss to St-Pierre at UFC 94 continues to haunt him, he said, adding that he always felt a third fight with GSP was deserved – and even discussed – at different times.

“Everything is in the past, but I’d like to get out there, show Tri-Star Gym and their fans or whatever that I’m a worthy opponent,” Penn said. “I’m not just a guy that will walk in the ring and somebody’s going to walk across and crush me.”

Photo credit: Daniel Herbertson/MMA Fighting