Ben Askren just showed he's dead serious about coming out of retirement to square off with his nemesis, Jorge Masvidal ... revealing he's been keeping in incredible shape despite being years removed from the UFC Octagon.
The former fighting star -- who's been retired from MMA since 2019 -- took to Twitter to show off his shirtless bod ... and to tell Masvidal he's now really ready for another scrap.
"I've kept in great shape during retirement," he said. "I have zero desire to fight anyone except that loser Jorge."
The two initially fought in the UFC way back in 2019 after months of trash talk -- and it was one of the most memorable bouts ever .