PITTSBURGH — Capitals center Jay Beagle suffered an undisclosed upper-body injury in the first period of Washington’s 3-1 win over the Pittsburgh Penguins on Sunday night. Beagle was ruled out for the rest of the game, and he’s not expected to play in St. Louis on Monday in the second game of the Capitals’ back-to-back set.

Coach Barry Trotz didn’t have an update on how serious Beagle’s injury is or how long he might be out — the team has just three regular season games left before the start of the playoffs — but said Washington won’t recall another forward before playing the Blues. That means versatile rookie Chandler Stephenson is likely to fill in for Beagle as the fourth-line center in St. Louis.

The Capitals secured first place in the Metropolitan Division for a third straight year with their win Sunday, so Washington can afford to be cautious with Beagle’s health. He hasn’t missed a game all season, skating 12:34 per game with a 58.6 faceoff percentage, the third-best in the NHL. Beagle also averages the most shorthanded time on ice of the Capitals’ forwards. The 32-year-old is in the last year of his contract, and he has seven goals with 15 assists.

Before Beagle retreated to the locker room with 4:39 left in the first period, Washington’s head trainer tended to him on the bench, rubbing his back and side.

Trotz has been experimenting with different combinations on his third and fourth lines over the past week to find which mix he likes most for the playoffs, and he indicated Beagle’s absence won’t be the only change to the lineup Monday. Trotz previously said the team intends to recall rookie center Travis Boyd before the playoffs, and if Beagle is still ailing, Boyd could be a potential replacement in the postseason.

“Tomorrow we’re going to probably have to put a couple guys in,” Trotz said after Sunday’s game. “Obviously, I’m not going to put Beags back in. We’ll see where we are health-wise, and we’ll get an opportunity to do that. But we still want to be playing well the last couple games.”

Read more on the Capitals: