The Bruins played well for 20 minutes on Saturday and looked determined to get back on the winning track. Against a lesser team and lesser goaltender, that might have been enough. Maybe even on Thursday when they played a shorthanded Florida Panthers team.

But Andrei Vasilevskiy (22 saves) stood tall when the Bruins controlled the game and the Tampa Bay Lightning scored three unanswered goals in the third period to beat the Bruins, 3-1.

It is the first time the B’s have suffered consecutive regulation losses since Dec. 21 and 23 and was the first time the B’s suffered a regulation loss after taking a lead into the third (31-1-4). The B’s, outshot 10-3 in the third, also went 0-for-4 on the power play.

“We had a few chances (in the second period), even in the first but I also thought the power play needed to step up. It didn’t really give us a lot of Grade A chances,” coach Marco Sturm told NESN. “But we were fine though. We were still good enough today but, again, those little details now, they matter and those details have been hurting us for two games in a row now.”

The Bruins took a 1-0 lead into the third period but it didn’t last long. The B’s got caught deep in the Lightning zone and allowed the Bolts to break out with numbers. Jeremy Swayman (19 saves) made the first stop and then Andrew Peeke’s desperate clear attempt went right to Charle-Edouard D’astous, who scored off his own rebound at 2:13.

The B’s got their fourth power play of the game at 4:31 on a D’Astous cross-check but they came up empty for the fourth time.

With the B’s generating little offense, the Bolts took their first lead of the game on a rare soft goal by Swayman with 5:31 left in the third. Darren Raddysh carried the puck deep and, without options, he threw it on net. It hit Swayman’s far arm and dropped in behind him.

Swayman, whose has gotten a total of two goals of run support in these first two games of the road trip, chose to accentuate the positive when asked about the goal.

“Any 2-1 game, you’re going to get goals that are magnified,” Swayman told reporters in Tampa. “It’s our job to move forward and really take positives. A lot of great things came out of tonight’s game, so that’s what we’ve got to focus on.”

Nikita Kucherov finished it off with an empty net goal.

Before the puck even dropped, it was a fairly eventful afternoon in the Eastern Conference playoff race. Two of the four teams that started the day six points behind the B’s, Detroit and Ottawa, both lost in regulation. The Red Wings’ lifeless loss to the Rangers also clinched playoff spots for the Lightning and Buffalo Sabres, who snapped a 14-year post-season drought.

Whether or not the knowledge that they had secured a playoff spot affected Tampa’s play early on, the B’s were the better team in the first two periods.

The Bruins had a chance to take the first lead of the game midway through the first period. Pavel Zacha’s shot from the right wing broke through Andrei Vasilevskiy and sat tantalizingly in the crease behind. Charlie McAvoy appeared to have a sure tap-in goal but Raddysh hooked him and kept him from pushing it over the line. Raddysh took a penalty on the play but it was well worth it. The Bolts were able to kill it off, even though a clock malfunction appeared to give the B’s a couple more seconds than the usual two-minute advantage.

When the officials spotted it, it created a lengthy stoppage to get the time right.

The B’s got one more power play late in the first but could not cash in then, either.

Shots were even at 8-8 in the first.

The again had another great chance three minutes into the second when Casey Mittelstadt sprung the B’s for an odd-man rush. Zacha then sent Viktor Arvidsson in alone but Vasilevskiy got a glove on Arvidsson’s backhander.

But the B’s finally broke the at 6:47 of the second on play that was equal parts pretty and hard-working. McAvoy carried the puck over the line and lost it with what he felt was an uncalled hook, but the B’s maintained possession and outworked the Lightning for several pucks. Eventually, Arvidsson found Mittelstadt steaming down the middle of the ice and Mittelstadt buried a wrist shot over Vasilevskiy’s blocker.

The B’s kept up the pressure. Vasilevskiy stoned Jordan Harris right in front of the net then, on the same shift, Nikita Zadorov clanged the post on a shot from distance.

The B’s got their third power play but again could not capitalize. With 11 minutes gone in the period, the B’s were holding a 10-1 shot advantage in the period but the lead remained one goal.

Fraser Minten gave the Bolts their first power play when David Pastrnak was rushing the puck and Minten could not get out of Pontus Holmberg’s way on the blue line, taking an interference. But the B’s were able to kill it off, thanks to a very good blocker save by Swayman on Oliver Bjorkstrand.

Slowly, Tampa started to warm to the game. They kept the B’s hemmed in their end for much of the final three minutes of the period. Swayman’s best stop came when he gave up a big rebound and it went right to Nick Paul. He circled to Swayman’s left but could not lift his shot over the netminder’s glove.

The B’s had 20 minutes to secure a victory over the Bolts. But the final three minutes of the second were a sign of things to come.