Capitals defenseman Mike Green has missed 33 of 43 games this season even before his latest setback, which may sideline him until late February. (Toni L. Sandys/THE WASHINGTON POST)

The Washington Capitals grew accustomed to playing without defenseman Mike Green early in the 2011-12 season, but on Monday they learned that they will be without the two-time Norris Trophy finalist until at least late February.

The team announced that Green will undergo abdominal surgery and is expected to miss four to six weeks, with the later timeframe projecting to around the NHL’s trade deadline on Feb. 27.

Green missed 23 games and 21 / 2 months after suffering a right groin strain in mid-November, then aggravated the injury in his second game back in the lineup. The surgery, which is scheduled for Tuesday, according to a league source, is to repair the damage from the now-chronic groin injury.

General Manager George McPhee was not immediately available to comment on Green’s status and the decision to move forward with surgery.

The Capitals, who had a tenuous grasp on the Southeast Division lead entering Monday night’s games, have struggled to fill the void left by their No. 1 defenseman. They are 9-1-0 with him in the lineup and 15-16-2 without him.

Green was forced to leave the game on Jan. 7 against San Jose after playing just 7 minutes 11 seconds when he re-injured his groin. At the time, Coach Dale Hunter said the defenseman was day-to-day. Five days later the defenseman was placed on long-term injured reserve and the news of his surgery comes just nine days after that contest.

This is the latest in what has been a year of injury woes for Green. The 26-year-old has missed 33 of 43 games this season with the groin injury and earlier a with a twisted right ankle.

Dating from Feb. 8, 2011, Green has appeared in only 20 of the Capitals’ 80 regular and postseason contests; he was unable to finish five of those because of injury.

“With Mike we’ve been dealing with that all season long,” Troy Brouwer said a day after Green left the San Jose game. “It sounds bad, but that’s nothing new. We’re used to it almost.”

Green initially injured his groin on Nov. 11 in New Jersey after he absorbed an awkward hit in the corner by Devils forward Ryan Carter.

The injury proved to be more severe than the Capitals initially anticipated, and when Green’s recovery plateaued the team became anxious and sent him to Minnesota to undergo an experimental electrical stimulation treatment called Accelerated Recovery Performance, according to several sources familiar with the situation.

When he was nearing a return from the initial groin injury, Green acknowledged the groin problem likely wouldn’t go away completely.

“I think I’m going to have to be cognizant of this for the rest of my career, probably,” Green said in late December. “It’s something you’ve got to take care of, especially with hockey it’s such a common thing.”

Green played 15:43 against Calgary on Jan. 3 before injuring the groin again in the next game.

It’s been an unfortunate turn in the past two seasons for Green, who led all NHL blue-liners in points in 2008-09 and 2009-10. He is in the final year of a four-year contract worth $21 million and is set to become a restricted free agent this summer. To retain Green’s negotiating rights in the offseason, the Capitals will need to submit a qualifying offer of a one-year deal worth $5 million.