Unlike last season, few people have the Bruins at the top of their Stanley Cup contender’s list, despite their position atop the NHL standings. And in truth, their performance on Tuesday was uneven.

But when David Pastrnak is at the top of his game like he was and you combine that with some timely, scintillating goaltending from Linus Ullmark, it’s enough to beat the Ottawa Senators.

Pastrnak notched a hat trick and Ullmark kept the damage to a minimum in a lopsided second period to lift the B’s to a 6-2 win at the Garden, their third straight victory.

The game started rather sleepily for the B’s and everyone else in attendance with two short delays for rink repairs by the bull gang.

But Pastrnak woke everyone up with a pair of goals (42, 43) in less than three minutes midway through the period.

The first one came at 8:27 when, parked in the slot, Pastrnak deflected Matt Grzelcyk’s slap pass past Joonas Korpisalo.

Then he turned defense into offense for his second goal. Wheeling in the B’s zone, Tim Stutzle attempted an ill-advised that Pastrnak picked off and pushed ahead for a breakaway. With a pair of Sens on pursuit, Pastrnak took it in tight and just got the puck to roll over Korpisalo’s blocker for the 2-0 lead at 11:23.

The B’s controlled play after that for the rest of the period but could not extend the lead.

And they didn’t make it easy on themselves early in the second when John Beecher was called for slashing and, after spending nearly the entire penalty kill in their own zone, Charlie Coyle was called for a dubious tripping penalty, giving Ottawa a 37-second 5-on-3. Ullmark, who made a couple of good saves early in the game as the B’s got their footing, had to be spectacular to keep the Sens off the board.

But when Andrew Peeke was called for interfering with Mark Kastelic on an Ottawa rush, the Sens finally got on the board at 13:08. On the Sens’ 21st shot of the game, Shane Pinto’s Grade A shot from the slot broke through Ullmark to make it 2-1.

When the B’s finally got their first power play at 17:15 after Jakob Chychrun interfered with Trent Frederic, who’d been getting under the Sens’ collective skin for a few shifts, they cashed in. After the first unit turned it over to the second unit, the B’s scoring on a simple play. Coach Jim Montgomery had been looking more of a shot mentality and he got. Kevin Shattenkirk got a shot on net that Korpisalo could not handle and big Justin Brazeau was there to deftly control the rebound and score on the rebound at 18:51.

But the B’s could not bring the two-goal lead into the second break. Ullmark spit out a rebound of a Chychrun shot and Brady Tkachuk pushed his way to the top of the crease to shove the puck home with just three seconds left on the clock.

It was a painful goal to allow, but one the B’s – outshot 23-11 in the second – probably deserved to be in a tight game.

But Pastrnak completed his 17th career hat trick at 4:43. Playing down low, Shattenkirk attacked the net and tried to get a pass through the Pavel Zacha but Korpisalo denied it with his stick, knocking it into the slot. Pastrnak homed in on it and beat Korpisalo with a backhander.

Twenty-five seconds later, Jesper Boqvist took a Beecher pass in the neutral zone, cut from right to left in the offensive zone and beat Korpisalo on a nice move to his forehand.

After nearly blowing a three-goal lead to Philadelphia on Saturday, the B’s were able to salt this one away with little drama. Brazeau added his second power-play goal of the game with 1:54 left to finish it off.