Pittsburgh’s Kris Letang defends against Boston’s Morgan Geekie during the Bruins’ 2-1 loss on Friday in Boston. Michael Dwyer/Associated Press

Well, you didn’t think those six goals the Bruins scored against the Islanders on Wednesday would be the start of something big, did you?

On Friday, the Bruins scored the first goal of the game before everyone was in their seats at TD Garden, then didn’t score again, losing to the Pittsburgh Penguins, 2-1.

Philip Tomasino scored the winning goal at 7:26 of the third and then Tristan Jarry (32 saves) shut the door to nail down the win for Pittsburgh. Jarry went into the game with a 4.34 goals-against average and an .868 save percentage, but you never would have known it on Friday.

While this might have been the worst defensive game of the five since Joe Sacco took over at interim coach, the Bruins’ goal-scoring woes remain their most troublesome issue. They got 33 shots, including 13 in the third period. David Pastrnak, who now has two goals in his last 16 games, fired the puck 15 times with seven landing on net, including one in the third period that caught the jersey of Jarry to deflect wide.

The offensive problems have been particularly pronounced at the Garden, where they’ve scored just four goals in their last four games.

“We scored six goals last game, so I don’t think it’s an excuse. We’re getting paid to put pucks in the net, right?” said Bruins defenseman Nikita Zadorov. “Obviously we had chances to get a lead, to tie the game as well at the end, and it just didn’t go our way. I feel like it’s been the story of our season so far. Hopefully it will turn around. We’ve got to get a couple of bounces.”

Bruins goalie Jeremy Swayman made 33 saves and looked good again, with nothing to show for it.

“I’m just sticking to my process, understanding I need to do whatever I can to help this team have a chance to win every single game, and that’s what I want to do, is give them a chance. And I know for a fact that we’re going to come through,” said Swayman. “Even if we score only one goal, I want to make sure we close games out. It’s a team game, obviously, but I’m really excited about what we’re doing and the process that we’re sticking to and I know the results will come.”

The first half of the first period was entertaining as both teams went up and down the ice, with too many odd-man chances for Sacco’s liking.

“We got caught up in a game that we probably shouldn’t play. It’s not to our strength,” said Sacco.

But it was the Bruins who cashed in on one of the early chances.

On a pretty tic-tac-toe play from the third line, Trent Frederic took a feed from Tyler Johnson, and Frederic in turn made a nice dish to a wide-open Charlie Coyle at the right circle. Coyle picked his spot under Jarry’s glove for his fifth goal of the season and first point in five games. It was Frederic’s first point in six games.

It was just 1:24 into the game, and it felt like this was going to be a 6-5 affair.

It wasn’t.

The Penguins started the second period with 1:39 of power-play time after an odd sequence. On a delayed penalty on Johnson, Evgeni Malkin was parked at the blue line in front of the Bruins’ bench. As he drifted away from the bench, his Russian countryman, Zadorov, nudged him with his stick. Malkin responded with a wild swing of the stick, which the refs caught. They had to go to the video to see who the Bruins culprit was and, sure enough, they nailed Zadorov. Both he and Malkin went off for two minutes apiece.

“We’re old friends,” said Zadorov cryptically, declining to elaborate.

Said Sacco: “We don’t need that penalty there.”

The Bruins killed off that power play, but the Penguins continued to test Swayman.

First, he had to made a quick pad save on a deflection off Charlie McAvoy’s leg. The rebound went into the slot, but Swayman managed to get a piece of Tomasino’s shot to deflect it over the glass.

A little later, Anthony Beauvillier had a clean look off the rush, but Swayman flashed the glove to preserve the Bruins one-goal lead that was looking slimmer by the minute.

He couldn’t hold the Penguins off forever. Even with a Bruins power play, the ice began to tilt in Pittsburgh’s favor until finally, with .8 seconds left in the period, the Penguins got the equalizer. Crosby collected an Erik Karlsson shot behind the net, circled and fed Rickard Rackell, who roofed it over a sprawling Swayman, who said he over-committed on Karlsson’s original shot.

Both teams had third-period troubles. The Penguins had been outscored 13-1 in the third in their previous eight games, while the Bruins had not scored a third-period goal at the Garden since the first home game of the season.

But the second-period trends continued in the third, and the Penguins took the lead at 7:26. Pittsburgh won several puck battles down low until Malkin fed Tomasino and, from the inside of the left circle, Tomasino’s off-speed shot beat Swayman through the pads.

“I think I got caught a little bit off-balance, so it was just a lucky break for them and it’s unfortunate,” said Swayman.

The Bruins had chances to even it, including on an unsuccessful power play with seven minutes left in regulation. Jarry made a great late save on a deflected Andrew Peeke shot, and then Karlsson stoned Elias Lindholm on the rebound. Coyle also had what looked like an open short side to stuff a puck home, but Penguins defenseman Kris Letang prevented it.

“Right now, it’s a situation where the puck’s not finding it’s way into the net,” said Sacco. “We had our chances tonight again. but you have to execute still at a higher level in order to finish off your plays. I’m not sure we got that done here tonight.”

Not according to the only place that matters – the scoreboard.