The No. 6 Boston University men’s hockey team earned a trip to the Hockey East Semifinals with a double-overtime victory over the University of New Hampshire Sunday night, but the game was not always a close one.

Just 4:34 into the second period, BU looked as though it was finished as far as the Hockey East tournament was concerned. The Terriers were trailing, 4-1, thanks to four unanswered goals that were capped off by a short-handed Mike Borisenok tally. The goal marked just the second time the Terriers allowed a short-handed score all season.

At that point, BU could not do anything right, including getting a shot on net. BU was being out-shot by a more than 3-to-1 ratio. The Terriers were not winning puck battles, and could not keep pucks on their sticks or out of their zone. The team was playing so poorly that some fans headed to the exits despite the more than 30 minutes remaining in the game.

And so, with BU struggling mightily at the time, BU coach Jack Parker called a timeout.

“We called a timeout and I’m thinking, ‘Boys, we could have went out to eat instead of showing up here. We could have had a dinner somewhere,’” Parker said. “I said, ‘You look like you were Friday night. You’ve got to sooner or later stop and start this game all over again because you look exactly like you played Friday night. You look like you’re lost. You look like you’re inept and you don’t know where you’re going. Let’s get going here boys.’”

BU did not start playing well immediately.

UNH killed off the rest of the BU power play with nary an issue and then junior forward Ross Gaudet took an elbowing penalty that the Terriers had to kill off. Following that penalty kill, junior assistant captain Justin Courtnall and the rest of the fourth line went out to generate some energy for a Terrier team that was being out-shot 23-6.

Courtnall almost single-handedly created that energy by laying a few big hits on the Wildcats along the boards, then followed the physical effort with two shots on net.

After Courtnall’s shift, the Terriers started buzzing. BU put 14 shots on net after, and scored twice in the period, tightening the game to a 4-3 UNH advantage at the end of two periods.

Junior forward Wade Megan erased the Wildcats’ lead when he tied the game 30 seconds into the third period, and BU continued to play hard for the next 47 minutes until junior assistant captain Alex Chiasson netted the game-winner 6:42 into double overtime.

“I think [the turnaround] all started with Courtnall, the way he was playing,” Chiasson said. “I thought he had a pretty big hit there in the second at one point. For some reason, the game just changed right there. We just happened to have more momentum. It feels like everyone got their legs back and everyone’s making better decisions. It’s funny how that happens, but that’s part of hockey and that’s why we play 60 minutes.”

The come-from-behind win seemed a fitting way for this BU team to earn a trip to the Garden. After all, BU has been a team all year that, when it looked like it was hopeless, somehow found a way to get back into games, the standings or the national picture.

The Terriers started the season in mediocre 3-4-1 fashion, but then won seven of their next eight games to finish the first half 10-5-1.

Over the break, BU lost its two top centers and leading scorers in then-senior Corey Trivino and then-sophomore Charlie Coyle. In its first game back since losing the duo, BU came out flat in a 5-2 loss to the University of Notre Dame. Then BU answered its doubters by running off five consecutive wins to move into first place in the national rankings.

Once BU seemed settled once again, it lost defenseman Max Nicastro following his arrest for an alleged on-campus sexual assault, marking the second time in the season a Terrier was arrested on sexual assault charges.

BU was down to six defensemen, but it responded by winning its next three games, starting with a 5-0 thumping over the University of Vermont.

In terms of actual games, BU has come from behind in nine of its last 15 wins.

According to Chiasson, BU’s resilience throughout the season has created a Terrier team that is now confident in itself no matter what the circumstances. It was that confidence, Chiasson said, that kept the team believing Sunday night.

“We were down 4-1 and I was on the bench and I honestly thought that we were going to come back for some reason,” Chiasson said. “This team has just been through so much and so much adversity that we believe in ourselves and we take pride of doing the right thing on the ice.”

Parker, who is now in his 39th season behind the bench, said the team’s resilience all season helped make the Hockey East semifinals berth that much more meaningful.

“I was really proud of this team,” Parker said. “After all the stuff they have been through, the guys that have disappeared from this lineup, people that have stepped up. The focus that they’ve had and the senior leadership that we’ve gotten has been . . . it makes me feel really good about what’s going on in that dressing room.

“They really deserved to get to the Garden, they really deserved to get to the national tournament. . . . We still are alive to have a chance to win the Hockey East Championship so I think that’s pretty nice.”