VANCOUVER — A week ago, the Washington Capitals were flying high as the only undefeated team left in the NHL. But two games, and losses, against Western Conference foes quickly brought them back down.

The Capitals return after being defeated 2-1 by the Edmonton Oilers and a sound 7-4 beating at the hands of the Vancouver Canucks, two distinctly different losses that illustrated weaknesses and areas that must be improved upon regardless of how good a start they had.

“You go off and you win seven in a row whatever and maybe things get swept under the rug a little bit because you’re kind of rolling,” Mike Knuble said after Washington succumbed to the Canucks on Saturday. “Always a good reality check at the beginning of the year. You’ve got to be on every night. Teams are ready for you, you’re not going to sneak up on anybody.”

Against the Oilers, there was a feeling of disappointment among the players in watching the franchise’s best start to the season end at 7-0 but Washington remained upbeat. They outplayed Edmonton, which was held to 12 even-strength shots, for long stretches but lost control of the contest when they fell into penalty trouble. When the Capitals managed to stay out of the box, they couldn’t seem to solve an outstanding Nikolai Khabibulin in net.

The message after losing to the rebuilding Oilers was to maintain perspective and bounce back. The Capitals were loose as they practiced twice at Rogers Arena before taking on Vancouver, which was anxious for a statement win in what’s been a rocky October.

Instead, Washington didn’t come close to matching the Canucks in either the first or third period. Bad defensive zone coverage and turnovers gave Vancouver continual opportunities, unnecessary penalties snuffed out the Capitals’ momentum and not even a goaltending switch could spark the team for more than the second period.

“This one we didn’t play well,” Dennis Wideman said. “We scored four but we were just bad defensively. Gave them a lot of chances in the slot, didn’t block a whole lot of shots, turned pucks over. We just weren’t sharp on our own end.”

Given how the Capitals — from Coach Bruce Boudreau to Brooks Laich — said they would need their best game of the year against the Canucks, it made the lack of follow-through all the more concerning. Defensive positioning, commitment to backchecking and staying true to assignments in their own end has been Washington’s biggest challenge this season.

Through nine games, these Capitals aren’t showing the same adherence to defensive principles that allowed them to become a more stalwart club in 2010-11 when they allowed only 2.33 goals per game (fourth best in the league).

Part of that has also been the drop-off of the penalty kill, which stands at 77.1 percent compared to last season’s second-best 85.6 percent success rate and recent rash of penalties. In the losses to Edmonton and Vancouver, the Capitals gave up a combined four power play goals on 13 tries. Boudreau criticized both the penalty killing and singled out the first three penalties against the Canucks as “lazy penalties.”

“The thing that really has to get better is our penalty killing, which was very good last year is really not very good right now,” Boudreau said. “We have to correct that. It’s put us in the hole well the both games we’ve lost it’s put us in a big hole and the games that we’ve won we’ve still allowed PK goals. So we’ve got to shore that up. We shore that up I think a lot of other things will take care of themselves.”