Kessel, Leafs jolt sinking Bruins

Call last Friday’s 6-1 rout by Detroit an aberration. If you want to be generous, consider Sunday’s rematch, a 4-2 setback to the high-flying Wings, a disappointing but expected loss to one of the league’s elite clubs.There is little rational explanation, however, for the Bruins’ 4-3 loss to the Maple Leafs last night before 17,565 at TD Garden. Not when you have a one-goal lead with less than six minutes remaining. Not when you have the league’s top goalie, if not the best player, supposedly locking down the doors.

Yet here the Bruins are, losers of three straight and curious as to where their lockdown defense and goaltending have gone.

“Unacceptable,’’ said coach Claude Julien. “It’s one of those situations where if you have any sense of pride, you’re embarrassed about tonight. Not because the other team played well. But because we did not play to the level we should be playing. Right now, that’s been creeping in with the types of goals we’ve been giving up. It’s unacceptable. It’s pretty simple. It’s unacceptable. That sense of urgency doesn’t seem to be there. At the same time, after that Montreal game, we really did look like a team. Tonight we didn’t. Starting from the game right after Montreal — the two Detroit games and now tonight. The mistakes we’re making are just unacceptable. It’s guys not thinking, not being ready. I don’t know if there are distractions up in the air that brings that around the team. To me, tonight’s game was a very big disappointment.’’

The identity of the 2010-11 Bruins, like the three previous iterations that Julien has coached, is defense. Rare are odd-man rushes, multiple scoring chances, or third-period meltdowns.

But in the last four games, the leaky Bruins have given up 20 goals. Thomas, asked to do more amid Tuukka Rask’s inconsistency, could be wearing down physically and mentally. The demands on Thomas may explain why he failed to save Mikhail Grabovski’s winning goal when he had stopped such shots with ease all year.

To start the winning sequence, Grabovski settled the puck behind his own blue line. With Patrice Bergeron offering only a brief flick of his stick for resistance, Grabovski hurtled through center ice and went one-on-two against Dennis Seidenberg and Andrew Ference. Grabovski’s speed prompted Seidenberg to fall, but Thomas was square and in position to stop the attacker’s bad-angle shot.

Thomas thought Grabovski was going five-hole. At the same time, Thomas was wary about Nikolai Kulemin, who had joined the rush and was going back door. Instead, with 61 seconds remaining, Grabovski went upstairs on Thomas for the winning goal. It was Grabovski’s second.

“You’ve got to take the body on skilled guys, or else they’ll dance around you,’’ said Thomas (24 saves). “But if they do get through, the goalie has to make some big saves. That didn’t happen tonight either