Aroldis Chapman will be out until at least the middle of September with a knee injury, the New York Yankees confirmed.
Yankees manager Aaron Boone told reporters the 30-year-old Yankees closer received a platelet-rich plasma injection (PRP) in his left knee on Friday.
Chapman – a five-time MLB All-Star and 2016 World Series champion – will be re-evaluated in two weeks.
"We're optimistic that he'll return in an impact way this season at some point," Boone said.
"I think in a lot of ways [the exam] went a little better than the doc thought."
Chapman left Tuesday's 2-1 win over the Miami Marlins in the 12th inning after feeling pain in his knee.
He was placed on the 10-day disabled with left knee tendinitis.
Chapman has 31 saves with a 2.11 ERA in 50 appearances this season.