PITTSBURGH – Washington defenseman John Carlson won’t play in the Capitals’ game against the Penguins on Monday night. Carlson didn’t play after the first period on Sunday afternoon against the Philadelphia Flyers because of an undisclosed “lower-body” injury, and though he traveled with the team to Pittsburgh, he wasn’t on the ice for the optional morning skate on Monday.

Capitals Coach Barry Trotz indicated Carlson’s injury is day-to-day and anticipates he’ll play in the team’s next game in St. Louis on Jan. 19.

“We’ve got a few days here before the next game, so he’s close, but I just think long-term, we keep him out tonight,” Trotz said. “I expect him to be ready to go [for the St. Louis game].”

With Carlson out, Taylor Chorney will be in the lineup, likely on a third defense pairing with Nate Schmidt. Trotz said Brooks Orpik would move up in the lineup, and he could be paired with Dmitry Orlov. That would then reunite last year’s top defensive duo in Karl Alzner and Matt Niskanen. The Penguins will also be missing their top defenseman on Monday night, as Kris Letang was put on injured reserve.

“We’ll probably move Brooks Orpik up into a few more minutes,” Trotz said. “He’s played very, very well for us. That’s probably what we’ll do there. We’ll mix them up during the game.”

Carlson left practice early Thursday afternoon, and the team said he was being evaluated for a lower-body injury. Trotz indicated Carlson’s ailment was not serious, saying that he just needed “a little maintenance” after Wednesday night’s game against the Penguins. Carlson played 20:42 in Friday’s game against Chicago.

On a Penguins power play in the third period on Wednesday night, Carlson blocked a Letang shot with his leg, and when asked if that was related to him leaving practice early Thursday, Trotz said “it’s related from playing in a hockey game.”

This will be the first game Carlson has missed this season, and he leads the team in time on ice per game with 23:17, playing on the first power play and penalty kill. With him not on the ice on Sunday, Niskanen manned the top power play unit, and defenseman Nate Schmidt was on the second unit.

Carlson missed 26 games last season with a broken ankle. He has five goals and 20 assists this season and has skated on a top defense pairing with Alzner. The Capitals have been the healthiest team in the league this season, as this is just their 11 man-game lost to injury.

>>> Capitals center Nicklas Backstrom has been named the NHL’s “first star” for the week, the league announced on Monday.

In a week that featured some dominant performances by Washington as the team extended its winning streak to nine games, taking over first place in the league, Backstrom led the NHL in assists (seven) and points (10) in four games.

He had multi-point games in all four contests, starting with one goal and one assist in a 4-1 victory over the Montreal Canadiens on Jan. 9. On Jan. 11, he recorded one goal and three assists in a 5-2 win over the Penguins, followed by one goal and one assist in a 6-0 win over the Chicago Blackhawks on Jan. 13. Backstrom finished the week by notching two assists in a 5-0 victory over the Philadelphia Flyers on Jan. 15.

Backstrom leads the Capitals in scoring with 12 goals and 30 assists for 42 points.

>>> How does Trotz explain Washington’s success against Pittsburgh this season? After the Capitals lost the first game in a shootout, they’ve won the past two by a combined margin of 12-3. This is the last regular-season meeting between the teams.

“We know each other pretty well,” Trotz said. “I couldn’t tell you exactly. We know that every night they’re going to come at you, and they’ve got lots of weapons. They force you to play a quick game, and I think our team has adjusted to play a quicker game playing them as many times as we did last year and again this year. We know each other pretty well. I don’t have anything specific for you, really.”

Washington had an optional skate at PPG Paints Arena, but here’s a guess at what the lineup will look like on Monday night:

Alex Ovechkin-Nicklas Backstrom-T. J. Oshie
Marcus Johansson-Evgeny Kuznetsov-Justin Williams
Brett Connolly-Lars Eller-Andre Burakovsky
Daniel Winnik-Jay Beagle-Tom Wilson

Karl Alzner-Matt Niskanen
Brooks Orpik-Dmitry Orlov
Nate Schmidt-Taylor Chorney

Braden Holtby (starter)
Philipp Grubauer

Chandler Stephenson