Buffalo’s Luke Adam fires a slap shot past Capitals’ goaltender Tomas Vokoun, who like many of his teammates was not at the top of his game Saturday night. (Dave Sandford/Getty Images)

The Washington Capitals arrived here with a backdrop that was uncannily similar to what they faced a week earlier in Toronto. Looking to respond from a poor outing in the previous contest, Washington prepared to face a Buffalo Sabres club decimated by injuries.

The Sabres were without nine regular players Saturday night, but just like the Capitals’ game against the Maple Leafs, the advantage in health didn’t make up for a disadvantage in determination as Buffalo handed Washington a 5-1 loss.

Washington (12-9-1) is 3-7-1 in its past 11 games and with each defeat come questions about changes on the roster or behind the bench as the team continues its downward spiral. The loss to the Sabres illustrated the Capitals’ recent tendency to crumble when faced with any sort of misfortune.

“Sometimes we’re not mentally strong,” Coach Bruce Boudreau said. “This group has got to learn how to be mentally strong. It hasn’t had a lot of adversity in the last four years unless it was in the playoffs. The regular season, it seems like it was a walk in the park. We’ve reached, for 15 games now, some adversity and some guys are having a tough time with it.”

The Capitals might have earned a reprieve from any alterations when they started the week with back-to-back wins against Phoenix and Winnipeg. But after two more listless defeats — on back-to-back nights — it’s clear their problems are not ebbing. General Manager George McPhee did not make the trip to Buffalo with the team, instead traveling to Hershey, Pa., to watch the Capitals’ American Hockey League affiliate. Boudreau, whose job security has been doubted with each stage of Washington’s struggles, was asked how a team finds its mettle.

“It’s got to come from within, I’ve got to believe,” the 56-year-old Boudreau said. “I’m hoping that’s got to come from within because if I’ve got to teach them how to be tough, then I don’t know quite how to do that.”

Signs of unraveling began in the final 10 minutes of the first period. Buffalo (13-9-1) took a 1-0 lead 10 minutes 47 seconds into the game when a clearing attempt by Dennis Wideman ricocheted off the stick of Sabres center Paul Szczechura and hopped out in front. Luke Adam, who was in the slot unguarded, fired a one-timer past Tomas Vokoun (23 saves).

Less than five minutes later, Jason Pominville put the Sabres ahead 2-0 after Vokoun got a piece of a shot and knocked the puck into the air. It fell on the left side of the crease where the Buffalo captain swatted into the cage.

This defeat, though, can’t be placed solely with Vokoun. Even at that early stage, the Capitals looked deflated and began letting the group of energized Sabres — with five recent members of their AHL affiliate Rochester Americans in the mix — skate circles around them.

“There’s definitely a lack of confidence,” defenseman Karl Alzner said. “You can see it in guys that are usually so confident with the puck and stuff that they do, and that’s hard to get back. It’s up to us as a team and coaches and everybody. We’ve got to give everyone as much confidence as possible. Especially through a stretch like this, everyone comes to the rink and they’re down. We get a goal scored against us and we’re down.”

The start of the second period appeared to offer a little hope for the visitors, who got on the board 6:39 into the period when Jason Chimera scored on a penalty shot. The 32-year-old winger roofed the puck past Jhonas Enroth (26 saves), cutting the deficit to one, but not even his ninth goal of the year could provide a sustainable boost.

Twenty-seven seconds later, the Sabres answered when Zack Kassian beat Vokoun five-hole. It was Kassian’s first career NHL goal in just his second NHL game, instead of a save the Capitals needed their key offseason signee to make.

At the start of the third, Buffalo increased its advantage to 4-1 when Adam scored his second goal of the game. After Szczechura won a battle in the corner against Nicklas Backstrom and Jeff Schultz, Adam skated into the slot, where Alex Ovechkin made no discernible movement to prevent the tally. Jochen Hecht added the final dagger for the 5-1 margin — the sixth time in 14 games that the Capitals have allowed five or more goals.

Ovechkin was on the ice for each of the final three Sabres goals and finished a minus-4, marking just the fourth time in his career, and first since Nov. 20, 2008, against Los Angeles, that he has finished a game with such a negative rating.

“I think it’s just frustration,” Ovechkin said when asked if there was a crisis of confidence among the Capitals. “Just frustration moment and when you have that kind of situation you just have to work, and if you’re going to be frustrated after when they score, you’re going to look sad about yourself. It’s not going to work.”

In the span of 48 hours, not only did Washington suffer consecutive losses but it was also outscored 11-4 and looked nothing like a team expected to compete for a Stanley Cup.

“I don’t know, it’s back to the drawing board and let’s see where we’re at,” Boudreau said. “We’ve got to get more consistent, better efforts from a number of people and it’s just something that the consistency is definitely lacking and we’ve got to find out the reason why.”

Capitals notes: Mike Green missed his eighth consecutive game with a strained right groin muscle. . . . John Erskine was out for a fourth straight game after falling on his surgically repaired left shoulder in practice.