BALTIMORE — A day after Dellin Betances gave up a walk-off home run to Manny Machado, the Yankees bullpen took another blow.

Adam Warren, who has been good to excellent in a variety of bullpen roles this season, was placed on the disabled list with lower back spasms on Wednesday. Joe Girardi didn’t paint an overly optimistic picture, saying the righthander, who has a 2.40 ERA in 45 games, will be out at least two weeks.

“I am [concerned],” Girardi said. “Right now the doctors recommended that he rests for two weeks. We were hoping we’d get him back here in Baltimore but we didn’t.”

Girardi said Warren, who last pitched Friday against the Red Sox, first complained of the discomfort Sunday night. Warren, who missed 17 games from June 16-July 3 with right shoulder inflammation, did not make the trip to Baltimore.

Girardi said he believes Warren will make it back before the end of the regular season but couldn’t guarantee it.

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“You would think as a reliever if in two weeks he’s physically OK, that you could get him back at some point,” Girardi said. “But that’s if he’s OK after two weeks.”

CC gets ‘maintenance’ injection

Late Wednesday afternoon CC Sabathia departed to the clubhouse to get a lubrication injection in his balky right knee, which caused him to spend time on the DL last month. Pitching coach Larry Rothschild said the shot was “maintenance,” and that Sabathia is expected to make his next scheduled start. The 37-year-old lefthander allowed five runs and eight hits over 5 1⁄3 innings of Tuesday’s 7-6 loss.

Extra bases

Clint Frazier, out since Aug. 9 with a left oblique strain, began a rehab assignment with Double-A Trenton Wednesday night and could be back sometime next week . . . Gary Sanchez will serve the final game of his three-game suspension Thursday and will be eligible for the Rangers series, which starts Friday in Arlington.