Mark Tibbs, trainer for former two-division world champion Billy Joe Saunders, said it was very difficult to stop the fight with Saul 'Canelo' Alvarez.
The two boxers were colliding in a unification clash for the WBC, WBO, WBA super middleweight titles.
Before a crowd of over 73,000 fans, Canelo stopped Saunders in eight rounds at AT&T Stadium in Arlington, Texas.
During the eight round, Canelo landed an uppercut that injured Saunders' right eye. The area began to rapidly swell up.
When Saunders went back to the corner, he advised Tibbs that his vision was impaired and he couldn't see from the right eye.
Tibbs made the tough decision of stopping the fight.
"It's never easy. It's never easy in a moment like that. But his leading eye was damaged and I've got too much love for the man to send him out there or ask him to go out there," Tibbs told IFL TV.
"For me, he was starting to build momentum. He got that eye socket - it looks broke to me - and then obviously, you know, the game falls apart. For me, I would've rather kept it long. Long and slick and awkward. Long, slick and awkward, that's what I wanted.
"But I guess Billy's got a fighting heart. Listen, when someone is walking you down like that, you've got to stand at times. It come off, actually. He put a good left uppercut and right hook or a right uppercut and left hook, one of the two. But he done well. But he done well up until the point he got injured."
Over the weekend, the 31-year-old Saunders underwent surgery after suffering a quadripod fracture to his right orbital bone.