Head coach Barry Trotz just announced that defenseman John Carlson is doubtful for the Capitals’ next game against St. Louis.

Last Thursday, Carlson left practice early. According to CSN Mid-Atlantic, Trotz described that injury as a lower body issue which required some “maintenance.” On Sunday, Carlson was unable to finish the Caps’ 5-0 thrashing of the Philadelphia Flyers. Carlson left the game in the first period. Later, the Capitals announced that Carlson was questionable to return after suffering a lower body injury. It’s unclear if Carlson aggravated the original practice injury or when the injury occurred.

Carlson traveled to Pittsburgh on Monday, but did not play.

During Wednesday’s practice, the Caps’ defense pairings looked like this.

Per NHL.com’s Tom Gulitti:

Niskanen-Orlov

Alzner-Chorney

Orpik-Schmidt

It’s unknown however which duo is the second or third pairing as The Washington Post’s Isabelle Khurshudyan reported Orpik and Schmidt were skating on the second pairing instead of Alzner and Chorney.

The Capitals lead the NHL in fewest man games lost to injury.

#Caps have by far fewest man games lost to injury this season with 11. Next closest is 43. I (delicately) asked Barry Trotz about it. pic.twitter.com/b6LH2nM63H — Stephen Whyno (@SWhyno) January 18, 2017

The team will consider recalling a seventh defenseman from Hershey as insurance, likely veteran Aaron Ness.

Carlson didn't practice today. Trotz says #Caps may recall D-man from Hershey tomorrow. Road trip with 12 forwards because "We have planes." — Stephen Whyno (@SWhyno) January 18, 2017

Last season, Carlson suffered a broken ankle that caused him to miss 25 games. He had surgery in late February.

“I hurt it, took some time off, tried to come back, it felt good, and then it kind of deteriorated,” Carlson said to CSN during the 2016-17 preseason.

“At that time,” he continued, “we just felt the only option was to get surgery and put some screws in it to basically bulletproof it, make sure that I was back in time for the playoffs and that we were not ever going to have an issue with it again.”