Fulmer got a second opinion Tuesday from renowned surgeon Dr. James Andrews after an MRI. He told reporters Wednesday that a third opinion confirmed the diagnosis.
"If you go to court for something and you're sentenced to basically the death penalty, you're going to want to try to appeal it, right?" Fulmer said, according to MLB.com. "It's the worst outcome possible, and I wanted to see another set of eyes just to see if he had any alternative."
Fulmer, 26, won AL Rookie of the Year honors and was an All-Star in 2016 but has struggled to return to that form. He was 3-12 with a 4.69 ERA last year, his season cut short in mid-September because of knee problems.
Injuries have played a big part. He underwent ulnar nerve transposition surgery on his throwing elbow in 2017. Last season, he underwent his third knee surgery.
Tigers manager Ron Gardenhire told reporters that the team will meet to figure out how to fill the vacancy in the starting rotation.
"You always plan for this," Gardenhire told reporters. "We have multiple starters. That's what we've said. Right now it's more about thinking about Fulmer than anything else. We'll take care of the baseball part and fill in a hole or whatever. Let's just see how it goes with him and see where we go with that, and we'll work from there. I feel bad for him right now more than anything else."