One of the AL West leader's top starters sustained a serious knee injury, tearing his left patellar tendon Wednesday against the Boston Red Sox
Richards was 13-4 with a 2.61 ERA this year. It's a serious blow to the Angels, who also lost starter Tyler Skaggs to Tommy John surgery earlier this season.
''You're going to be thinking of Garrett once every fifth day when he was out there,'' manager Mike Scioscia said Thursday. ''You might not be able to replace that, but it doesn't mean that we're not going to be able to reach our goal as a cumulative pitching staff.''
General manager Jerry Dipoto said ''we'll be open'' about finding a deal to replace Richards in the rotation.
Richards crumbled to the ground covering first base on a potential 3-6-1 doubles play against Boston. He was taken off the field on a stretcher and was flown to Los Angeles on Thursday morning, where he had an MRI.
The Angels tweeted Richards will have surgery on Friday. The rehabilitation time should be six to nine months.
The Angels selected the contract of left-hander Wade LeBlanc, who pitched briefly for the New York Yankees earlier this season, from Triple-A Salt Lake. Richards was placed on the 60-day DL to make room on the 40-man roster.