For the Boston Bruins to hold on to the final Stanley Cup Playoff spot in the Eastern Conference, goaltender Tuukka Rask is probably going to need to play like the Vezina Trophy winner he was last season.

For that to happen, Rask will probably need the Bruins defense to revert, and stick, to its signature stingy ways.

Well into his worst season statistically since becoming Boston's No. 1 goaltender, Rask is honest about how his game suffered early this season. The frank Finn talks openly about the link between his poor start and a defense that lost Johnny Boychuk to trade on the eve of the season, captain Zdeno Chara to a knee injury for 19 games three weeks after the season started, and Adam McQuaid to a finger injury from mid-November to the New Year.

Rask didn't excuse his own role in the early stumbles, saying he felt good but the Bruins needed more and he "just wasn't able to be great out there." Like most things surrounding goaltending, Rask's performance through January did not exist in a vacuum.

"I've always played my best when I am aggressive and challenging," Rask told NHL.com. "But when you have new guys on the back end trying to find their game and comfort zone, it makes the goalie's job different too. You can't be as aggressive as you normally are because you have to be ready for passes to the backdoor and loose pucks that normally get cleared. There's been a lot of that."

It's not like Rask has been terrible this season.

His save percentage has climbed to .919, which was good enough for No. 12 in the NHL. But that is a full percentage point below any total of the past three seasons, and well off a career .928 save percentage coming into the season which was on pace to be the highest of all time, above Dominik Hasek's .922.

Rask's play has been trending in the right direction with Boston two points ahead of Florida for the second wild card.

Before McQuaid came back Jan. 3, Rask had a .907 save percentage. Since the New Year, Rask has a .932 save percentage despite some wobbles during Boston's recent six-game losing streak.

"His play at the beginning of the year, I don't think we made it easy on him with our play and the injured players and the quality of injured players we had," coach Claude Julien said. "It put a lot of pressure on him and he probably didn't get the same protection he has had lately, but still, having said that, his game has gotten better too."

With help from Double Blue Sports Analytics and their soon-to-launch 360 Save Review System 2.0, NHL.com took a look at some of the shot-quality data to see how Rask's recent run of good play compared to the scoring chances he saw earlier this season.

Not surprisingly, the quality has gone down lately.

The numbers from Double Blue don't include the past five games (the cutoff was the Feb. 13 game at the Vancouver Canucks), but it's pretty easy to see how the shots Rask is facing have changed.

Rask's goal locations (Click to enlarge)

Through the end of December, 39.4 percent of the shots Rask faced were considered Grade A based solely on shot location. (Grade A chances are defined as coming from within the home plate area in front of the crease, out on an angle to the faceoff dots, and then up to the top of the faceoff circles). Since Jan. 1, the percentage of Grade A shots is 35.6. At the same time, Rask's save percentage on Grade A shots rose from 83.9 percent to 87.7 in the New Year.

As Rask is quick to point out, it's not just where a shot is coming from that matters. It's also the type of play which generates the shot.

"The scoring chances have gone up," he said, " but it's the type of scoring chance you give up too that makes a big difference."

Here too, there is a measurable difference in 2015. Keeping in mind some shots can be counted in multiple categories, the number of screen shots, deflections, one-timers and shots off lateral passes all decreased during the past two months. Deflections made up 23 percent of the shots before the New Year, and 8.7 since, and the percentage of screen shots dropped from 17.5 to 8.7.

It's more than seeing more good chances. It's about how seeing certain types of chances consistently can change how a goalie plays.

It's not a secret, nor somehow shameful, that the Bruins' defensive structure under Julien, which stresses eliminating the cross-ice passes and all plays which force a goaltender to reset laterally, has typically benefitted the goalie.

Look no further than the numbers put up by past backups Chad Johnson (.925 save percentage in Boston, .890 since leaving for the New York Islanders) and Anton Khudobin (.926 in Boston, .917 since leaving for the Carolina Hurricanes) for proof. Tim Thomas knew he couldn't play as aggressively after leaving the Bruins with a Stanley Cup, Conn Smythe and two Vezina Trophies because other teams wouldn't be able to cover off those tendencies.

Rask's save locations (Click to enlarge)

Rask admitted he thought about changing his game.

"Early in the year some things you didn't even think could be possible happen and it's like, ‘There's nothing I could have done,'" he said. "Get enough of those and you start to think, ‘What do I do differently?'"

As a goalie it's easy to start cheating to the pass on odd-man rushes after enough get through; or leaning off the near post because you are worried about a back-door threat; or staying deeper in the crease because you aren't as confident a rebound will be cleared so you need to be able to return to your post sooner. At the NHL level, it doesn't take much of a cheating lean in one direction for a shooter with time and space to exploit the goalie the other way.

"That becomes an issue in the back of your head," Rask said. "You start cheating for that pass."

The Bruins are counting on those thoughts being out of Rask's head down the stretch, but how they play defensively will determine how far out of the thought process they really are.