Defenseman Mike Green, who has missed 52 of Washington’s last 62 regular season games with various injuries, is undergoing ARPwave electrical stimulation therapy in an attempt to recover from his latest ailment, a strained right groin. (John McDonnell/The Washington Post)

As the Washington Capitals step on the ice in Buffalo on Monday evening they will do so with a much too familiar vacancy on their defense. The game against the Sabres will be the 20th consecutive and 26th of the season without Mike Green in the lineup.

Over the past two seasons, Green’s absence from the lineup has become a new normal for Washington and a trying time for the two-time Norris Trophy finalist. Dating from Feb. 8 of last season, Green has missed 52 of the past 62 regular season contests because of injury.

It’s unclear when Green, who was not made available to comment for this story, will return from his latest setback, a strained right groin muscle that he suffered in mid-November. When Green’s recovery plateaued two weeks ago, the Capitals decided to take an experimental route with his rehabilitation, according to several people familiar with the situation who requested anonymity because they were not authorized to discuss the defenseman’s recovery.

Green received Accelerated Recovery Performance (ARP) treatment, which involves electrical stimulation, in Minnesota, according to those people. It’s unclear whether Green, who skated for five days prior to the NHL’s holiday break, has benefited from the program.

But while Green’s teammates, coaches and agent, as well as Capitals’ officials await his return, all say the groin injury will not pose a significant threat to the defenseman’s career. But there’s no denying that the steady string of ailments have had an impact on it.

“The last two years, he’s had a lot of things go wrong — the concussions, now the groin and the foot,” said Nicklas Backstrom, one of Green’s close friends on the team. “I think he’s trying to be as positive as he can and get back as soon as possible, but it’s tough for him. You can see he’s frustrated. I feel bad for him and I want to see him play hockey again. That’s all he wants to do.”

In the 2008-09 and 2009-10 seasons, Green led all NHL defensemen in points. But in the two years since, he has been sidelined by injuries to his shoulder, knee and hip flexor, a pair of concussions, a twisted right ankle and now the groin strain. The limited playing time has kept Green, 26, from continuing his evolution as a player, whether that would have included becoming a consistent two-way presence or continuing to dominate with his offense.

It’s possible that Green’s lack of durability could result in a pay cut. The Calgary native will earn $5 million this season in the final year of his current contract, a four-year deal worth $21 million, and become a restricted free agent this summer. In order to retain Green’s negotiating rights in the offseason, the Capitals will need to make a qualifying offer of a one-year deal worth $5 million.

Green played his best game of this season on Oct. 22 when he tied his career high of four points in a single contest in Washington’s 7-1 win over Detroit, but he missed the next six games with the twisted ankle. Less than eight minutes into his return to the lineup, on Nov. 11, Green was hit in the corner by New Jersey’s Ryan Carter and suffered the groin strain.

“Mike’s missed more significant time than he would have liked recently, but it’s beyond his control — beyond anyone’s control,” said Craig Oster, Green’s agent. “He was very excited about starting the year and taking another step personally, and as a team. The part that is encouraging, in all of these unfortunate circumstances, is that none of the injuries have been of a real significant variety that should have any lasting impact on Mike’s ability to play in the long term.”

Green’s groin injury came not long after the Capitals lost Tom Poti to persistent groin problems. Poti was among the team’s top three in ice time for three seasons before he played in just 21 games in 2010-11. There is no sign that Poti, who is under contract through 2012-13 but not with the team, will play again and while Green’s injury is not believed to be as severe, it’s difficult not to draw parallels as his absence lengthens.

Green was making progress in his recovery from the groin strain when he slammed his stick into the boards on Dec. 8 as he went off the ice. Shortly after that incident, which the team insisted wasn’t a setback, the Capitals sent Green to Minnesota, according to people familiar with the situation.

The program involves a machine called the ARPwave, which sends electrical current through targeted areas of the body in conjunction with controlled movement, to help promote recovery from injury. The ARPwave is not widely used, but is growing in popularity among professional and college athletes to speed rehabilitation, keep muscles relaxed and refresh tissue.

According to league sources, Capitals’ assistant general manager for player personnel Brian MacLellan owns and uses an ARP­wave machine. Boston goaltender Tim Thomas is one player who has publicly acknowledged his use of the system and thanked its developers when he accepted the Vezina Trophy in 2011.

There remains no timetable for Green’s return, but when he does the defenseman will have two new coaches and must adapt to a new system of play. Green has attended team meetings and video sessions under Coach Dale Hunter and worked with assistant coach Jim Johnson, but it remains to be seen how he will fit into a style of play that doesn’t encourage as much offensive risk-taking as former coach Bruce Boudreau’s approach.

Of the 82 goals and 250 points Green accumulated in his career, he recorded 76 and 229, respectively, with Boudreau behind the bench.

“He’s been involved in all our meetings, he knows exactly the way we’re playing and he understands what we want to do,” Johnson said. “When he gets closer we’ll spend a little more time with him on the ice, get him more involved in the practices. . . . We all want Mike back in the lineup, but only when he’s 100 percent. It doesn’t help us to rush him only to have something else go wrong.”