"We thought we were past it," Melvin said. "He got a cortisone injection but at some point in time that kind of dissipates."
Phegley received the injection in May while dealing with right knee discomfort, and was placed on the DL retroactive to May 10 with a knee sprain and returned May 27. He said he felt no issues with the knee until after Friday's game against Pittsburgh, a game he started, when he awoke Saturday morning with discomfort.
Phegley watched video of Friday's game to see if a specific play triggered the discomfort, but couldn't find anything. He went 0-for-4 in a loss but said he felt no issues while playing.
"We're trying to figure out what's going on," said Phegley when asked if he was concerned. "I'm just a little confused I guess. Hopefully we can find some answers."
He's batting .256 with a home run and 10 RBIs in 78 at-bats, primarily appearing against left-handed pitching, and was hitting .130 over his last eight games. He'll be sidelined through the All-Star break at the very least.
Oakland recalled catcher Matt McBride from Triple-A Nasvhille to take Phegley's spot. McBride was listed in the A's lineup Sunday.
It's McBride's third stint with the A's this year. He's batting .228 in eight games with Oakland, and hit .306 with four homers in 23 games since being optioned to Triple-A May 27 following a two-week stay with the A's.
Mark Chiarelli is a reporter for MLB.com based in the Bay Area.