ST. PAUL — After two weeks off, the Boston University hockey team looked rusty, not rested, and its season came to a quiet end.

Denver took a four-goal lead just 23 minutes into Saturday night’s NCAA West Regional semifinal game, cruising to a 7-2 victory and dashing the Terriers’ hopes of a return to the Frozen Four.

“When you lose 7-2, you certainly lose to the better hockey team and I thought that was the case tonight,’’ Terriers coach David Quinn said.

While thanking his seniors, who were sophomores when he took over for legendary coach Jack Parker, Quinn broke down and was comforted by captain Matt Grzelcyk.

Having not played since falling to UMass-Lowell, 5-0, in the opening round of the Hockey East playoffs March 12, the Terriers were energetic early but couldn’t solve Pioneers goalie Tanner Jaillet.

“The first five or 10 minutes I thought BU was the better team and we were playing nervous,’’ Denver coach Jim Montgomery said. “After that I thought our penalty kill gave us a lot of momentum and we started managing the puck well and playing our game. Offensively it was probably one of our best nights.’’

Things got worse for BU on the other end of the rink, as Denver took a 2-0 lead by the end of the first period on goals by Blake Hillman and Dylan Gambrell.

“It kind of snowballed on us,’’ Grzelcyk said. “Coming into the second period we still had a chance and there was still plenty of hockey left, but I think we played a better team and they capitalized on their opportunities. It got to a point where it was too much to handle.’’

The Pioneers began the second period on a power play, and a seeing-eye shot from the blue line by Will Butcher made it 3-0 just 24 seconds in. That one was not only the eventual game-winner, it seemed to deflate the Terriers.

“They got an early power-play goal, and that’s obviously tough,’’ Grzelcyk said. “You could see guys heads go down and we kind of lost belief starting there.’’

When Matt Marcinew made it 4-0 less than three minutes into the middle period, Quinn called time out and lifted goaltender Sean Maguire, replacing him with Connor LaCouvee. Maguire finished with nine saves on 12 shots.

“It gets to be 4-0 early in the second period, you can’t fault [Maguire] on it, but you’re looking for a momentum change, you’re looking for something to spark your team,’’ Quinn said. “We felt we still had a chance at 2-0, if you can kill that penalty off . . . but you give up that third goal and you could kind of feel it.’’

Evan Janssen’s goal made it 5-0 for Denver (24-9-6) before the second period was over and Butcher added another power-play goal in the third.

BU finally broke the shutout with just over seven minutes left when Danny O’Regan cleaned up a rebound. But Denver answered on the next shift, sapping any momentum for BU. Mike Moran got the Terriers’ second goal with just 14.7 seconds remaining.

Quinn said his team never fully recovered from a 1-0 loss at Notre Dame on Feb. 27. They went 2-3 the rest of the way, losing their final three games of the season to finish with a 21-13-5 mark.

“I wish I could explain how our season kind of unfolded here after that Notre Dame loss,’’ Quinn said. “We played well the second night at Notre Dame and it cost us a bye. We just never recovered from it. We just weren’t able to bottle the confidence and the mental toughness that you need at this time of year.’’

LaCouvee finished with nine saves for the Terriers. Jaillet had 19 saves for Denver, which will face fourth-seeded Ferris State on Sunday with a trip to the Frozen Four in Tampa at stake.

The Bulldogs upset top-seeded St. Cloud State, 5-4, in overtime in the opening game on Saturday.