The good news for the Bruins on Tuesday in Dallas was that their leading goal scorer Morgan Geekie finally snapped his 12-game goal-less streak.

The bad news? Everything else that happened.

The B’s had their six-game win streak snapped on Tuesday in Dallas — and they left no doubt about it. In one of their worst performances of the season,  the B’s — outshot 37-18 — were dominated by the Stars in every meaningful category and dropped a 6-2 blowout.

The B’s took three first-period penalties and were gashed on two of them in the final four minutes of the first. From there on, they were simply non-competitive.

There was little in a micro viewpoint to be taken from this one. But coach  Marco Sturm, whose team lost 39 of 60 faceoffs, believes his team will be better for the drubbing in the long run.

“The positive is that we actually got pounded today,” Sturm told NESN. “It shows me and hopefully everyone that…these guys play in the playoffs every year. They were playing that grinding game. They didn’t have a good start because they were losing lately. For us, we were not willing to play that grinding game. That was the difference. And what it shows us is that that’s something we have to learn if you want to be like the Dallas Stars and be in the playoffs every year. We’ve got to be willing to grind every night and every period, from the top players down. That’s the positive for me today, because we’ve got work to do.”

The two teams entered the game going in different directions. The B’s had won six in a row and were 8-1-1 in their previous 10, while the Stars had lost three straight and were 2-6-2 in their previous 10. On top of that, the Stars were without one of the best players in the league, Mikko Rantanen, who was out of the lineup with an illness.

The teams, however, would both make abrupt U-turns.

Some of the Bruins’ bad old ways cropped up in the first period and, because of it, they found themselves in a 2-0 hole going into the first break.

The game was pretty even for the first 15 minutes, with both teams exchanging unsuccessful power plays and there was a brief Jonathan Aspirot-Nathan Bastian bout.

But thanks to penalties late in the period, everything fell apart.

Elias Lindholm took a shaky neutral zone interference penalty on Esa Lindell and the second-ranked power-play went on their second advantage. From the right point, Roope Hintze pulled Jeremy Swayman out of his net with the threat of a shot and Hintze sent a diagonal pass down low to Wyatt Johnston and the one-timer into a wide open net at 16:08.

Then came the killer. Nikita Zadorov took a defensive zone cross-checking penalty with 2:05 left in the period. They were close to surviving and getting to the room down just a goal, but they could not. Swayman made a spectacular stick save on Mavrik Bourque at the side of the crease but he couldn’t control the rebound and Bourque scored on the put-back with 13 seconds left in the period.

“Those penalties, we just can’t take,” said Sturm. “Our top guys cannot take those kind of penalties.”

Thanks to the power plays, the Stars held a 15-6 shot advantage in the first period.

A 2-0 deficit against the Blackhawks is one thing. Down a deuce to a much better defensive team like Dallas is a much bigger hill to climb.

The B’s had better possession to start the second and stayed out of the box, but they could not generate much in the way of high danger chances.

Then the Stars took a three-goal lead on a low percentage shot. Coming out of the first TV timeout, the Stars won a faceoff in the Boston zone back to Lindell at the blue line and he simply threw a shot on net. Swayman was possibly screened and the shot beat him to the short side past his blocker for a 3-0 Dallas lead at 8:26.

There was still a lot of hockey to be played. But with the way this game was trending, the B’s were not going to erase that deficit, not with the way the Stars were protecting the house in front of goalie Jake Oettinger. The B’s continually failed to get pucks behind the Dallas defense and, as result, they couldn’t get their forecheck going.

And just in case anyone had any hope of a comeback in the third period, Justin Hryckowian made it 4-0 with 31 seconds left in the second, kicking a puck into the crease from the side of the net. It went off Mark Kastelic’s stick and slipped through Swayman’s pads.

At that point, the B’s were being run out of the rink, getting outshot 32-11. And it felt every bit as lopsided as that.

In the third, Jason Robertson scored a pair of goals in the first 6:37, the second one chasing Swayman in favor of Joonas Korpisalo.

“He kept us in there longer than we deserved,” Hampus Lindholm told reporters in Dallas.

To their credit, they didn’t totally fold. The B’s avoided their first shutout loss of the season when, on a power play, Geekie scored his 26th of the year when he deflected home a David Pastrnak shot. Fraser Minten added his 12th of the season but this one was long decided.

The B’s will spend Wednesday traveling home from Dallas and then have a quick turnaround to play the Vegas Golden Knights on Thursday at the Garden. However they choose to look at this game — as  a throwaway or as fuel — they will have to relocate their game in a hurry. They don’t want to start another wrong-way streak.

Loose pucks

The Bruins placed left-shot defenseman Vladislav Kolyachonok on waivers on Tuesday for the purpose of sending him to Providence. … After missing Saturday’s game in Chicago, Andrew Peeke returned to the lineup against Dallas.