(AP Photo/Nick Wass)

Defenseman John Carlson had an unspecified procedure on Saturday for a lingering lower-body injury, and he’s expected to be out of the lineup for “three to four weeks,” Capitals Coach Barry Trotz said.

“He’s out for a while,” Trotz said. “He had a procedure, just to take care of that sort of nagging thing he had all of the time. He’s going to probably be out for a couple of weeks here.”

Carlson missed 12 games earlier this season, and with the injury wasn’t healing as the team expected, the Capitals opted to take another step for Carlson to be 100 percent healthy entering the playoffs. He was a full participant at Friday’s morning skate, but then didn’t in the game.

The team declined to specify the nature of the lower-body injury. Carlson is expected to be placed on long-term injured reserve, which means Washington will have his salary cap hit of approximately $4 million off the books. That frees the Capitals to make a significant move before Monday’s trade deadline.

Defenseman Mike Weber practiced with the team for the first time on Saturday, so even with Carlson out, the Capitals have seven defensemen. Carlson has six goals and 25 assists this season, but Trotz admitted last week that Carlson wasn’t the same player since he returned from the injury in the last game before the all-star break.

“I’ve got a lot of respect for Carly because he was trying to get back so quickly after that,” Trotz said last week. “You can tell it was affecting his play. Even when he came back, he didn’t have the same pop. I respect him for coming back as quickly as he did to try to help a defensive corps that was pretty banged up, him included. That’s probably the thing you respect the most.

“I think it’s been a little bit of an adjustment period because what happens when you get an injury like his, even your posture and how you skate is a little different. He seems to be a little straight-legged a little bit more at times. It’s starting to come back now, as you get deeper and further away from your injury. It does affect your gait, in terms of how you skate, which affects your passing skills, which affects everything. Everything just gets off. It’s like having a rib out. You know, you just don’t have the same gait or you don’t move as fluidly.”

This is how the defense pairs looked the first time around on Saturday in practice:

Karl Alzner-Matt Niskanen

Brooks Orpik-Dmitry Orlov

Nate Schmidt-Taylor Chorney