WASHINGTON — There is one decision on defense awaiting Alain Vigneault’s attention before the playoffs commence in Montreal next week, in which the coach likely will choose between sitting Nick Holden, Brendan Smith or Dan Girardi for Game 1, given the effectiveness of the Kevin Klein-Marc Staal pair over the past three contests.

But there also is a decision to be made regarding the 12th forward spot. That one, in which Tanner Glass and Pavel Buchnevich apparently are vying for a uniform, is as much about style and fit as it is about personnel and skill.

That’s because Glass is a grinder who, in limited action since his March 5 recall from the AHL Wolf Pack, has had an impact on the Rangers’ often negligible forecheck game. He is the fourth-line rough edge on a team as smooth as a pane of glass who provides muscle on the forecheck with Oscar Lindberg and Jesper Fast. He represents a missing piece.

Buchnevich, on the other hand, is a finesse forward who has had a tough time finding a fit on the fourth-line unit with which he presumably would skate in the tournament, even as he was up on the first unit with Chris Kreider and Derek Stepan while Mats Zuccarello was one of six varsity players who sat out to tend to minor health issues for Wednesday’s Game 80, no-drama and no-stakes 2-0 loss to the Capitals.

Glass and Buchnevich both skated in this one, which officially locked in a Rangers-Montreal first round and clinched the Capitals’ second consecutive Presidents’ Trophy and third in the past eight seasons. Included among the missing for the Rangers were Zuccarello, Holden, Fast, Ryan McDonagh (for the third straight game since the playoff-clincher), Rick Nash and Brady Skjei.

“If our situation were different where we needed the points, they could all play,” Vigneault said. “Not every [team] is in this situation. I think it will help a little.”

Injuries aside, it is unlikely Glass and Buchnevich would both dress against the Canadiens, who remain skilled, but added some size and grit at the deadline in Steve Ott (who does not dress for every game) and Dwight King. It is even more unlikely that Brandon Pirri or Matt Puempel could get the call.

“Of course I’m playing for a spot for Game 1 and the playoffs. I think a few of us are,” Glass told The Post after turning in a solid 11:01, in which he was credited with a team-high four hits. “And I think my attributes are a little bit different than the guys I’m competing with.

“I’ve been in a few playoff series and it’s important that when push comes to shove, you have pushback. I play a solid defensive game and finish my checks. Those are important parts of playoff hockey. Plus, I had a coach in Winnipeg named Claude Noel who told me that my game is taking away my opponents’ game.

“They’ve got some guys who like to cut across high in the zone. So if I can come up with a hit on [Alexander] Radulov or another of their players, maybe I can have an impact that way. It’s not always what you do with the puck.”

Glass may be part of the present, but he will not be part of the Rangers’ future as he completes his three-year, $4.35 million contract prior to unrestricted free agency. Buchnevich, of course, is projected as a significant part of the franchise’s future as he completes his first season in North America with an upside still as high as the sky.

But the Russian rookie’s time probably is not now with Round 1 approaching. Even as Vigneault — who has prematurely gone into his playoff mum-mode, revealing nothing of his thoughts about or plans for the rematch of the 2014 conference final won in six by the Rangers — likes to jam as many skilled players into the lineup as possible, the tournament represents the time for jam.

So, although the decision on defense is a challenging one, the call on the 12th forward doesn’t seem especially confounding at all.