The sudden mean streak in standout center Marco Rosa, Merrimack’s best all-around player, cost the Warriors dearly in their upset bid against second-ranked Maine on Sunday.

Rosa was whistled for three penalties in Sunday’s matinee — twice within the game’s first 21 minutes — and the Black Bears capitalized on two of them on their way to a 4-2 victory in front of 4,616 inside a lively Alfond Arena.

Maine senior Lucas Lawson scored both power-play goals to raise his team lead to 17, as the Black Bears recovered nicely from a bitter home loss to Boston College on Friday to pull even again with the Eagles atop Hockey East.

The Warriors (11-12-5, 6-9-3 HEA), meanwhile, lost out on a bid to jump over idle Massachusetts into sixth place. Providence is now four points ahead of Merrimack with Sunday night’s win over New Hampshire, while the Minutemen hold a slim one-point lead with three more league games played than the Warriors.

“We didn’t do a lot of little things right, and they worked their tails off,” said Merrimack head coach Chris Serino, complimenting Maine’s start-to-finish solid performance. “The thing that makes me mad, though, is if we do a lot of the little things right we have a chance to win this game. But if you don’t, you have no chance.”

Entering the weekend with only eight penalties in 27 games, Rosa has been called for five over the last two. The junior was sent to the box twice in the third period of Friday’s 3-1 win at home over Northeastern, the second of which led to a Huskies’ power-play goal.

“I’ve got to play grittier and help the team out in that way, but at the same time I can’t be taking stupid penalties,” said Rosa, showing signs of frustration amid a four-game scoreless streak.

“I got unlucky a couple of times and didn’t mean to do what I did. But they need me on the penalty kill more than anyone, and I know that. I’ve got to stay out of the box and help the team out in that way.”

Coming out of the first intermission with a 2-1 lead, Maine received an immediate boost from Lawson’s second goal, which came off a Francis Nault rebound that goalie Joe Exter couldn’t smother. The senior lifted a backhander under the crossbar at the 2:28 mark.

But the backbreaker for the Warriors came just 1:02 later, as Black Bears freshman defenseman Steve Mullin one-timed a textbook Cameron Lyall pass from behind the net past Exter (23 saves) for his first career goal. It was Maine’s third goal in a 4:04 span.

“It was a big game for a lot of reasons,” Black Bears coach Tim Whitehead said, “most important of which was sending a message to ourselves that we belong at the top of this league. Unlike Friday night, we played smarter today. We tried to do too much Friday and it cost us.”

Although Maine (22-4-4, 12-3-3) held a territorial advantage in the first period, Merrimack limited the Black Bears’ scoring opportunities with some timely checking in close to Exter. The attention to detail in their own end paid off at the 13:25 mark at the other, as the Warriors scored the first goal for the first time in the three-game season series.

Senior Ryan Cordeiro stepped in front of a careless pass by Maine defenseman Troy Barnes at the home blue line, deflecting it toward the right wing where linemate Tim Reidy picked it up. The junior forward skated in uncontested on goalie Frank Doyle before snapping off a quick shot that sailed under the freshman’s glove for his seventh goal of the season.

But the lead was short-lived. Lawson netted his first of the game on the man advantage just 56 seconds later with Rosa off for hooking. Maine claimed the lead for good with only 44 seconds left in the period when senior Chris Heisten snapped in a rebound of a Colin Shields flutter shot on Exter that the Warriors captain was forced to play with his blocker.

“Defensively we were bad,” Serino said. “We were just bad.”

Junior defenseman Tony Johnson cut the deficit to 4-2 at 11:08 of the second period with a slapper from 25 feet out that Doyle (13 saves) was late getting his glove on. Although not giving up another goal over the last 36:30 of the game, Merrimack could generate just five shots over that same span.

“In the offensive end, we didn’t fuel their attack,” Whitehead said. “They are very good in transition and the neutral-zone play. It was big for us to control the puck like we did.”