Their lineup thinned by injuries, the Bruins ran off four consecutive victories recently by giving great efforts against the Kings, Sharks, Devils and Penguins. Many players were getting opportunities and took advantage, as all four lines skated and worked hard from minute one through minute 60.

But in the NHL, that formula – winning with all-out 60-minute efforts – isn’t going to work every time for the simple reason human beings can’t deliver that level of effort in every game. There are bound to be emotional dips.

And collectively the Bruins suffered one in Sunday’s 4-2 loss to the Edmonton Oilers, a nice game for the beleaguered, underachieving Oilers, who were much better than the Bruins in the important areas of skating and forechecking.

It was a significant slip for the Bruins, who now must rediscover their winning formula in a hurry with the Eastern Conference-leading Tampa Bay Lightning at the Garden on Wednesday.

The Bruins then head out for games in Philadelphia and Nashville, two big, physical and skillful opponents, so this could be a very dangerous stretch for a team facing a tough challenge to climb into a playoff position.

“We have to learn from the mistakes and try to get back on track, because the stuff that we did the last four games, it was like we didn’t do all of it (Sunday),” said Bruins winger David Pastrnak.

Pastrnak opened the scoring Sunday on the power play, but it was the Oilers who quickly seized control. They forechecked effectively and the Bruins generated little, getting outshot 27-11 in the first 40 minutes.

“It seemed like we lacked energy in the first couple periods,” said Pastrnak. “We weren’t throwing many checks. When your legs aren’t moving you can’t hit those guys and you can’t meet the puck there. Then they’re playing with more energy and they’re playing with the puck.

“I think the first two periods we definitely lacked energy. (In) the third, we started doing things better.”

Indeed, the Bruins found some redemption in the third, as they began to skate and attack with more purpose, if not any result.

“Lately we’ve been playing with a lead,” said defenseman Torey Krug. “And it’s almost like you take your foot off the gas, good teams are going to put pucks in the back of the net and change the momentum of the game.”

Sunday, there obviously was a spotlight on Tuukka Rask, playing for the first time in 11 days after watching backup Anton Khudobin play quite well in winning four successive starts. Rask would have liked another shot at the first Edmonton goal by Patrick Maroon, but otherwise played well enough to win. Instead, his record slipped to 3-8-2.

His teammates fully understand that the longtime star is going through a difficult stretch.

“Obviously he wants to win hockey games, (and) it doesn’t matter how,” said Krug. “We got to do a better job of playing for him and getting that win. Tie game, third period, in our home building, a good chance to get him going again. We came out there and let him down.

“He’s a competitive guy. He’s our No. 1 goalie. We got to come out there with a better effort for him and realize how important it is. We got to get the result for him. It doesn’t matter how. We just couldn’t do it.”

After a day off, the Bruins likely will learn whether Coach Bruce Cassidy will stick with Rask against Tampa Bay or go back again to Khudobin’s hot hand.

It may not matter.

For the Bruins to have any chance, they’ll have to skate and compete a lot harder than Sunday.

Also, the Bruins returned forward Jordan Szwarz to Providence.