Merrimack managed to keep BU’s top two scorers from notching a point in Friday’s 1-1 tie between the two teams.

Tonight? Not exactly.

BU forwards Danny O’Regan and Jack Eichel factored in all four goals as No. 3 BU topped No. 18 Merrimack, 4-2, in front of 4,366 at Agganis Arena. O’Regan notched his first collegiate hat trick along with an assist, while freshman sensation Eichel basically set up all four goals.

O’Regan now has 11 goals, one more than any BU player had in the whole 2013-2014 season. The Terriers’ 10 wins also match the team’s win total for all of last year as well. Eichel leads the nation in both assists (17) and points (25), while O’Regan is tied for second in goals and tied for third in points (21). Brian Christie scored both Merrimack goals.

After managing just four first-period shots last night, BU came out flying with 17 shots on goal and a whopping 40 shot attempts in the first frame. The Terriers looked loose and confident, also playing perhaps their most physical game of the season to date.

“I thought it was a completely different game than last night,” BU coach David Quinn said. “Last night we wouldn’t shoot the puck; we wouldn’t pass the puck. Tonight, I thought we did both of those things very well. I thought our puck movement was as good as it’s been in a while.

“Tonight I just think the guys were ready to go. They knew what was at stake; they knew that they wouldn’t play another league game for more than a month, so they were going to have to live with this for a while.”

Merrimack coach Mark Dennehy believed his team could have been more prepared for the adversity of a tough road game.

“I thought we actually got off to a pretty good start for the first five minutes, and then I thought we didn’t do as good a job of taking care of the puck as we needed to,” Dennehy said. “We didn’t talk enough about playing a good road game, and we didn’t play a good road game.”

BU, which had only scored four first-period goals in its 14 games of the season, got one tonight at 11:00. Ahti Oksanen slipped the puck to Eichel breaking into the zone on the left-wing side, and the freshman threaded the puck over to O’Regan crashing the net from the right-wing side. O’Regan slipped the puck onto his backhand and went right around goalie Collin Delia.

“The energy in the room beforehand, you could tell it was a different game for us,” freshman defenseman Brandon Hickey said.

On their next shift, Eichel made another great feed to O’Regan, and that was almost another goal. Instead, BU piled up shot attempts, but didn’t score again until the second period.

Regardless, BU put up another 17 shots in the second period, scoring on three of them this time. Just 16 seconds into the period, BU made it 2-0. Eichel held the puck along the left-wing boards before passing all the way over to freshman John MacLeod above the right-wing circle. MacLeod shot, and the puck was redirected in. Initially, MacLeod was credited with the goal, but the scoring eventually was changed to O’Regan on the tip.

On the next shift for BU’s top line, the Terriers scored again. This time, Eichel teed up Hickey for a wrist shot that beat the screened goaltender. It was Hickey’s first collegiate goal.

At 11:01, Cason Hohmann appeared to make it 4-0 for the Terriers when he banked a shot off of a defender and right around the goal line. It was called a goal on the ice, but a video review apparently showed that the puck did not cross the line.

Merrimack made it 3-1 at 14:49, just six seconds into a power play. Quinn Gould got the puck behind the BU net and threw it in front, where it seemed to carom off of Christie and go in.

The Terriers continued to play hard and got that one back at 15:51 on the prettiest goal of the night. Eichel looked over his shoulder as he chased the puck into a corner before backhanding the puck into the slot with his back to O’Regan, who crashed the net for the one-timer and the goal.

“When they get it going, there’s blood in the water,” Dennehy said. “They’re drooling. I thought as the game went on, their competitive level increased, and we didn’t respond the way I’d like us to.”

Given that the scoring change on the earlier goal didn’t happen until after the period, there were no hats thrown on the ice after what proved to be O’Regan’s third goal. However, the left winger was still pleased to pick up the Terriers first hat trick since Matt Nieto managed the feat on March 1, 2013, against Vermont.

“It was awesome, really exciting,” O’Regan said. “I was lucky enough to be in the right spot the right time and benefit from some really good plays from my teammates.”

O’Regan almost picked up a fourth goal during four-on-four play early in the third period, but Merrimack continued to hang in there for much of the third with some help from a five-minute major called on BU defenseman Dylan Somerby for hitting from behind. The Warriors failed to capitalize on that, but made it 4-2 at 14:15. BU goalie Matt O’Connor made a great initial save on Hampus Gustafsson when he was all alone on the doorstep, but the rebound squirted onto Christie’s stick for the easy goal on the rebound.

“A great weekend; three points in Hockey East is a great weekend, especially when you beat a team of that caliber,” Quinn said. “To play 10 league games and only have one loss is a great accomplishment, but there’s a lot of hockey left. This league can change in a hurry, and we’re aware of that. But we feel good about where we’re at in the league up to this point.”

BU (10-3-2, 7-1-2 Hockey East) plays on the road against Rensselaer next Saturday, while Merrimack (10-5-2, 4-4-1) doesn’t play again until January 2, when the Warriors play Minnesota in the first round of the Mariucci Classic.