PHOENIX -- Brewers closer Devin Williams could tell his lingering back issue had returned on the first day of Spring Training, when all he did was play catch and lift.

“I had a big flare-up,” Williams said. “It completely locked up the first day I got here.”

So when spine specialist Dr. Robert Watkins diagnosed two stress fractures in Williams' back on Wednesday, it did not catch him by surprise.

Williams said he will be shut down for six weeks, after which he will begin a rehab program that is expected to keep him off the field for another six weeks or so.

Another Spring Training, if you will.

“It’s going to be a build-up process, probably about another six weeks of throwing before I can get back into games,” he said. “Not picking up a ball for six weeks, it takes time to build up after that. We’ll see what it is when we get to it.

“Three months [in total time missed], in the grand scheme of things, is not really that long. I’d obviously rather be playing, but I’ll do my best to make sure it heals up correctly and I am back out there with the guys.”

Williams, named the Trevor Hoffman Award winner for being the best reliever in the National League in 2023, pushed through the initial pain this spring and resumed throwing bullpen sessions.

But he did not appear to be himself in his two Cactus League appearances, giving up four runs in 1 1/3 innings. He said his second outing against San Francisco on March 5 raised a red flag.

“It really started to bother me,” he said. “I started compensating, and my shoulder was getting sore in places that I don’t get sore because I’m compensating. So that’s when I said we need to get this checked out.”

Williams’ injury was extremely difficult to diagnose, he was told, because it occurred in his T12 thoracic vertebra, which is located near the bottom of the rib cage. Watkins told him most stress fractures are found in the lower L4-L5 region, the vertebrae that are on the lumbar spine roughly adjacent to the hip bones.

Williams said he felt back pain down the stretch last season but continued to take the ball as the Brewers moved toward their NL Central title.

“I remember feeling pain in my back in September, like going to warm up, and things just didn’t feel right,” he said. “But I just figured it was some muscle soreness or tight muscles, things like that. I was able to pitch through it.”

The discomfort was “not too bad, not to the point I needed to be out, but I didn’t feel good. We play through stuff all the time. Nobody feels 100 percent all the time, and it was September. That’s par for the course.”

The offseason did not provide as much relief as he hoped.

“There would be good days and bad days getting treatment and preparing for the season like usual,” he said. “I didn’t really think much of it.”

This will not be his first injury-induced absence. Williams missed the 2017 season after undergoing Tommy John surgery. He expects to rehab with the team during the season.

“I’ll be there cheering the guys on,” he said. “If anybody needs any advice or help with anything, I’ll be there just trying to help out in any way I can.”

He said he is confident the Brewers have the arms to fill the role at the back end of the bullpen.

“We have a lot of guys who can set up in that role, a lot of high-leverage arms that are in our bullpen right now,” he said. “Those guys will do their thing and pick me up while I am out.”