Two of the most intriguing words in all of sports are “if” and “necessary.” 

If necessary, a series can go five, six or seven games. If necessary, a team that’s a win away from advancing might need two or three games to do it. 

For the Bruins, their season comes down to “if necessary.” There’s either going to be a hockey game or nothing at The Garden on Wednesday night. The B's and the NHL have got it booked, and thousands of fans and media have arrangements to be there. But that’s only if necessary. 

What’s necessary for the Bruins as they face what would be a shocking first-round elimination at the hands of the Capitals is Boston’s best game of the season. While most of the regular season was spent in some sort of slump for the Bruins this season, they were, when at their best, unlike any other team in the NHL. 

They blew teams out regularly in December and January. The biggest way in which they let down the fans in their Jan. 5 meeting with Calgary was when they took a 9-0 victory despite the Garden’s clear “We want 10!” chants. 

The Bruins need their offense – the deepest in the league during the regular season as they were the only team in the NHL with six 20-goal scorers – to flex its muscle and give Braden Holtby a hard time. Surprise, surprise, but when the Bruins drove to the net in the second period on Brad Marchand’s goal, they scored. When Dennis Seidenberg got a clean look against Holtby, he scored. When the Bruins have been able to muster the opportunities they got with ease in the regular season, they’ve made Holtby look like an AHL goaltender rather than the phenom his clean saves have left him touted as. 

On Saturday, the Bruins got better chances against Holtby. The 22-year-old rookie made his best save of the series when he robbed an improving but still-not-there Tyler Seguin in front in the third period. That was one of two golden opportunities Seguin got late in the game. He also missed the net on a later chance, but the good news is that he’s been more engaged and gotten the opportunities. On Sunday he’ll need to bury those chances in order to make Wednesday’s game necessary. 

Seguin is just one example of many, of course. David Krejci needs to hit the net when he has Holtby screened with bodies in front and the B’s driving to the goal, as was the case on a second-period play on Saturday. The Bruins’ offense needs to click as a whole, as just two of the six aforementioned 20-goal scorers have gotten to Holtby this series: Chris Kelly and Brad Marchand, each with one goal. 

For the Bruins, it’s necessary that Tim Thomas be in 2011 postseason form. In a series in which goals have come sparingly – the average of 4.2 goals for each team per game makes this series the third-lowest scoring one in the postseason thus far –  the man who was good enough to have “The Save” on Steve Downie in Game 5 of last year’s conference finals rank right up there with Dave Roberts’ “The Steal” in Boston sports history must do it again. He needs to be air-tight. No getting beaten cleanly glove side on a wrist shot from Troy Brouwer, as he did on the play that decided Saturday’s game, and no big rebounds to an awaiting Mike Knuble. Thomas, like the rest of his teammates, needs to have his best game. Unlike most others in the history of hockey, Thomas’ best game means something that will be talked about for weeks, and maybe – if he can pull out the same type of stops (pun certainly intended) as last spring – forever. 

Defensively, the Bruins need to work with what they have. They need Zdeno Chara to continue to find ways to get bombs through to Holtby and they need to hope those shots can yield rebounds with willing forwards in front. If Joe Corvo can’t play after a blocked shot forced him from the game Saturday, Mike Mottau will need to step in as though he hasn’t spent the first five games of this series wearing a suit rather than a sweater. 

As a whole, the Bruins’ blue line needs to be the stingy force it’s been known to be in recent seasons. That means trusting Thomas to stop Jay Beagle rather than contesting it too late and forcing the puck to skip into the Bruins’ net. 

The Bruins were 1-2 in Game 6's last season, but the good news is that the one win came the only time they really needed it. Boston led both the Canadiens and the Lightning in their respective series before dropping the sixth game. When trailing the Canucks, 3-2, in the Stanley Cup finals -- the only series in which they trailed entering Game 6, the B's beat Vancouver with a 5-2 win. That was at the Garden, though. Both of Boston's Game 6 losses last postseason came on the road. 

If the Capitals are to take Game 6 on home ice and eliminate the Bruins on Sunday, it would go down as a greatly disappointing season, sandwiching the team’s 2011 Stanley Cup victory between a catastrophic blown 3-0 series lead and a first-round exit against a team playing with a first-year NHL coach and an AHL goalie. They can prevent that by turning in an effort Sunday that’s reminiscent of last spring mixed with this season’s November and December.

“We’ve got an opportunity tomorrow to get back into this series and create a Game 7,” Bruins coach Claude Julien said after the game, “and that’s what we’re going to try to do.”

For the sake of the 2011-12 Bruins’ legacy, it’s necessary.