But with five losses in his last six fights, it looks like the 44-year-old legend of the sport has reached the end of the line.
In his return to middleweight, Henderson, the former PRIDE and Strikeforce champion lost by TKO in just 1:10 to his fellow former Strikeforce light heavyweight champ.
The end came when Mousasi rocked Henderson with a right hand that clipped him in the temple. In the aftermath, with Henderson down on the mat and against the fence, Mousasi hit him with a right hand which appeared to briefly put Henderson out.
After the referee stepped in and waved the bout off, Henderson vigorously protested the bout shouldn't have been stopped.
Mousasi, for his part, held off for a bit before the referee waved off the fight, believing Henderson went out.
"I landed a good shot, but I stopped because he was already out," Mousasi (36-5) said.
Henderson (30-13) has dropped five of his past six fights.
"He fought a good fight, I got hit with a jab or something and I couldnt see out of my left eye," said Henderson, whose left eye was swollen shut. So he started pointing at it, he clipped me a little bit, but I was aware the whole time."