Jaromir Jagr lost the battle last night. Then he won the war and maybe the Eastern Conference finals for his new team the way he once did for the old one whose heart he broke just before the stroke of midnight.

The gray-bearded Jagr was, like everyone else on the ice as one day began to turn into the next, exhausted when he began battling the Penguins’ muscular Evgeni Malkin for the puck along the sideboards near the red line during what had become an interminable overtime fight for absolute control of who would go on to play for the Stanley Cup sometime next week.

For a moment, Jagr lost control of the frozen rubber, whose whereabouts would decide both teams’ fate, to Malkin, but before Bruins reinforcements could come to his aid, Jagr took things back into his own incredibly strong hands and not only poked the puck away from Malkin but got control of it. Jagr then sent the puck quickly and perfectly up to Brad Marchand, who knew where it was going next.

A second or two later, Marchand had moved the puck along toward a streaking Patrice Bergeron for a perfectly angled redirection past helplessly sprawling Penguins goalie Tomas Vokoun at 15:19 of the second overtime period for a 2-1 victory at the Garden. The win gave the Bruins a commanding 3-0 lead in the series and Jagr a reminder of the old days, when he was wearing the Penguins colors and helping to lead them to two Stanley Cup championships so long ago kids like Marchand have to see watch the highlights on YouTube to believe there once was a Jagr before this burly old man who stormed around the Garden last night like he owned it.

Being a 41-year-old hockey player in the NHL qualifies you for immediate membership in AARP, although over the last few playoff games Jagr has played nothing like someone who is ready to hang up his skates. He seldom appears ready to skate away from the game.

Jagr often embarks on training skates wearing a weighted vest after a game is finished. Last night was no exception, despite the fact the game became the seventh-longest in B’s history with 35:19 of overtime added to the game’s first three periods before Jagr’s hands and unbreakable will started them on the way to the winning goal.

As a crowd swelled around his locker, a team equipment man parted the multitude and lifted the top of Jagr’s locker seat, removing from storage the weighted vest he wears on those postgame skates and leaving silently with it.

If Jagr had something to say he would be saying it only to himself, but there was a statement to be made with that weighted jacket, those solitary postgame skates and most of all the way he outfought Malkin for the puck to register his 196th career playoff point, tying him with Paul Coffey for fifth place all-time.

“It was first of all a great play by Jags to take that puck on the wall there and just fighting and getting the loose puck to Marsh,” Bergeron said. “I think he’s got that experience I guess to always be at the right place on the ice, and on that play it’s just a perfect example that he’s buying in and wants to help in any way he can. That play right there we don’t get a goal if he doesn’t make that play.

“He’s pretty much a legend. He’s a guy that’s going to be in the Hall of Fame at some point and he’s doing the little thing right there just to fight for the puck. You notice that as a teammate and it goes a long way.”

Over time — and in overtime — things change. Jagr is not what he once was, but after starting on the third line when he first arrived in a late-season trade with the Dallas Stars, he now spends most of his time skating with Bergeron and Marchand on the second line, controlling the puck along the wall so long at times you want to holler, “Pass it!’’

Last night he did pass it, notching his third assist in the past two games and reminding everyone not only who he once was but how that came to be.

“I watched that whole Rangers (conference semifinal) series, and when you sit up in the stands I can honestly say in that series (Jagr) could have been our top scorer,” defenseman Andrew Ference, who sat out the five-game elimination of New York with an injury, said. “He put himself in a lot of really good positions, created a lot of plays and got snake bit. He’s changed his game a bit, obviously, not only as the years have gone on but coming to our team.

“A couple of huge plays he made grinding it out on the wall. That’s not going to make any highlight reels when he’s inducted into the Hall of Fame, but those are huge plays to win hockey games for us.”

That’s what Jaromir Jagr did last night. He did the dirty work that won a hockey game.

Then he put on a weighted jacket and skated silently away, lost in thought, preparing to help win the next one.