Milwaukee Brewers closer Devin Williams was diagnosed with two stress fractures in his back and is expected to miss around three months, sources told ESPN on Wednesday, a significant blow for the National League Central champions, who were relying on a deep bullpen to buttress a lack of high-end starting pitching.

Williams, 29, is a two-time NL Reliever of the Year and owns a career ERA of 1.89. With the trade of All-Star starter Corbin Burnes to the Baltimore Orioles and All-Star starter Brandon Woodruff out for the season following shoulder surgery, the Brewers' bullpen was a weapon on which first-year manager Pat Murphy could rely.

Now, he'll have to do so without Williams for the foreseeable future. Back specialist Dr. Robert Watkins diagnosed Williams with stress fractures on the left and right sides of his T12 vertebra, sources said.

While Williams is expected to make a full recovery without surgery and return midseason, he'll be shut down from throwing for six weeks and then start a slow buildup, sources said.

Williams' back issues started in September, but with Milwaukee in the midst of a pennant race, he pitched through them. Following Milwaukee's wild-card series loss to Arizona, Williams took a month off before starting his offseason program. His back showed no issues coming into spring training, but it flared up during his first bullpen session and required treatment. During his second spring training outing, in which he allowed four runs in two-thirds of an inning, Williams noticed the back pain affecting his throwing mechanics and underwent an MRI.

Watkins saw potential stress fractures, and further imaging Wednesday confirmed pars fractures -- which come from repetitive stress -- on both sides of Williams' back, sources said.

Though the Brewers boast a deep array of relievers, including right-handers Abner Uribe, Joel Payamps, Trevor Megill, Bryse Wilson and Elvis Peguero as well as left-hander Hoby Milner, Williams is unquestionably one of the best in baseball.

A two-time All-Star, he won the NL Rookie of the Year award in 2020, allowing one run in 27 innings during the COVID-shortened season. He made his first All-Star team in 2022 and repeated the honor last year, going 8-3 with a 1.53 ERA in 58 innings. With 87 strikeouts, 28 walks and just 4 home runs allowed, Williams -- whose Airbender changeup is regarded as one of the best pitches in Major League Baseball -- won his second Trevor Hoffman Award as the best reliever in the NL.

Williams, who was the subject of trade rumors throughout the winter, is due to make $7 million this season and will be a free agent after the 2025 season.