The Brewers fired bullpen coach Stan Kyles and promoted minor league pitching coordinator Lee Tunnell.
Kyles had been with the team in that role since 2009.
"It is important that we make every effort to try to improve our bullpen performance," Brewers general manager Doug Melvin said in a statement. "While Stan is not solely responsible, I felt that this change was the first step and was necessary. Stan has been a loyal member of the Milwaukee Brewers organization for 11 years. His hard work and dedication has been an integral part of the Brewers' success and is greatly appreciated. His professionalism, personality and knowledge will be missed."
The Brewers' bullpen has a 4.80 ERA and 15-26 record this season, leading the majors in losses and blown saves with 20. Opponents are batting .274 against Milwaukee relievers, which ranks 29th in MLB.