Fifteen months after stepping aside as general manager, Matt Klentak is leaving the Phillies.

Klentak, who had one year remaining on a three-year contract extension, will join the Milwaukee Brewers as a special assistant, a major-league source said Sunday night, confirming a report from The Athletic. His departure comes one month after former team president Andy MacPhail’s contract expired.

The Phillies hired Klentak to replace Ruben Amaro Jr. and lead a rebuilding project after they bottomed out at 99 losses in 2015. But the 41-year-old’s five-year tenure was marked by two things: no winning seasons or playoff appearances despite a skyrocketing payroll and a farm system that stagnated.

Klentak abdicated the GM role after the Phillies went 28-32 in the pandemic-shortened 2020 season. He stayed with the organization as a strategy and development officer, a newly invented position, but was not involved in baseball operations in Dave Dombrowski’s front office.

With the Brewers, it seems likely Klentak will have more input in baseball decisions as a resource for president of baseball operations David Stearns and general manager Matt Arnold. Before the Phillies, Klentak worked in the front offices of the Colorado Rockies, Baltimore Orioles, and Los Angeles Angels, as well as for Major League Baseball’s labor relations department.

The Phillies appeared to be headed in the right direction in 2018, when they made a 14-game improvement in Klentak’s third season on the job and under his handpicked manager Gabe Kapler. They sped up the rebuilding process by trading young shortstop J.P. Crawford in a package for Jean Segura and pitching prospect Sixto Sánchez for J.T. Realmuto, and spending nearly half a billion dollars on free agents Bryce Harper, Andrew McCutchen, and David Robertson.

After finishing 81-81 in 2019, they doubled down in free agency by signing Zack Wheeler and Didi Gregorius. The moves for Harper and Wheeler, in particular, worked out well. But the Phillies struggled to graduate their prospects to the majors, an issue that persists two years after Klentak’s demotion.

Klentak also did not support the firing of Kapler after the 2019 season. When the Phillies fell short of the playoffs again in 2020, it’s possible he would have been let go if he hadn’t relinquished the role.

“Matt had a pretty successful track rate with free agents. We just haven’t been able to bring up the people internally to support them,” Phillies managing partner John Middleton said when Klentak stepped down. “We just haven’t produced the guys. We haven’t produced the talent yet, and that’s a problem that’s haunted us.”

Assistant general manager Ned Rice is the highest-ranking club official who remains from Klentak’s front office. Bryan Minniti, the other assistant GM under Klentak, and farm director Josh Bonifay were let go in August.