Santana, 41, said after the loss that his body is old school, but that his BJJ is still sharp.
He explained that he's most proud of his crisp submission game, but felt it was time to hang up the gloves after falling short in the standup at Bellator 98.
"As time goes by, you start to feel things more and more until you feel it's time to stop," Santana said after Bellator 98. "After training for years, the body starts to complain about the injuries that pile up. I told everyone I was fine for this fight, but actually I had an injured arm and ribcage from sparring in Rio de Janeiro. This rib injury, especially, really affected my training. But it was an accident. I thought I broke a rib, but gladly that wasn't the case. It was the cartilage. These things happen. When I came back from Rio, I tried to continue training but I couldn't all I wanted."
Santana nearly submitted Butcher in the opening frame, but the latter's standup proved to be too much to handle.
"I am happy with my performance," Santana said after falling short against Butcher. "My jiu-jitsu worked, as it always does. I was able to control him well on the ground. When we traded on the feet, that didn't go so well. But I am happy. I had a good career. I represented jiu-jitsu for real, from the heart."
Santana competed until age 41 and he hopes to leave a lasting legacy.
"I wish to serve as an example," Santana said. "I want to be a good example for those kids learning the sport. If they see something in my game they like, by all means, use it. What doesn't work so well, they don't have to use. I also wish to be an example of good diet, health and longevity."
Santana's final victory was against Brendan Sequin at Bellator 82.