On the 34 power plays the Bruins allowed during the first seven games, their opponents tucked 10 pucks behind Tim Thomas and Tuukka Rask. The Bruins killed penalties at a miserable 70.6 percent success rate. The PK was perfect just once (3 for 3 against Dallas Oct. 16). Appropriately, the Bruins won that game at American Airlines Center, 3-0.

But as the Bruins have picked up their game recently, they’ve elevated their shorthanded performance. In their last 10 games, a run that coincided with the acquisition of Daniel Paille from Buffalo Oct. 20, the Bruins have given up only one power-play goal (against Detroit Nov. 3 in a 2-0 loss at Joe Louis Arena). They have killed off 28 of the last 29 chances and have upped the success rate to 82 percent, 13th best in the NHL.

In the last two games, the penalty kill has been at its best. Last Saturday against the Sabres, the Bruins brushed off seven Buffalo power plays. On Tuesday against Pittsburgh, they went 2 for 2 against the Penguins, adding a shorthanded goal in the third period when Patrice Bergeron floated in a long-bomb empty-netter.

They have been successful for different reasons.

Against Buffalo, the Bruins didn’t give the Sabres many chances to set up and take advantage of their first-unit talent (Thomas Vanek in the slot for tips and rebounds as the primary threat). The defensemen stayed tight in front of Rask, while the forwards were effective at clearing pucks down the ice. That way, the PK units could make crisp shift changes - ideally, each player is out for 25-30 seconds of maximum effort - without getting caught in odd-numbered situations.

“You can’t complicate the PK,’’ said Andrew Ference. “It’s about having good positioning, jumping on loose pucks when they’re available, and having the smarts to change well and have the energy so the next guys can go out and be aggressive as well.

“When it’s going bad, you tend to overcomplicate, getting caught out there too long, and not having the ability to jump on loose pucks and be aggressive because your legs are dead.

“[Against Buffalo], we had a bunch in a row where we had three or four different pairings of D go out within one single penalty kill, which is great. We’re out there for 30 seconds each. You’re full of energy. The next guy’s full of energy.

“When you get caught out there, it’s pretty hard to jump on loose pucks or pressure guys. They just end up becoming a shooting gallery.’’

The Bruins weren’t as successful against the Penguins in clearing the zone. After a first-period tripping call on Vladimir Sobotka, Zdeno Chara, Derek Morris, and Paille got caught out for nearly the entire two minutes. But the Bruins kept their PK box tight to conserve energy, and while the Penguins won puck battles against the walls, the penalty killers stepped in front of Pittsburgh shots. Chara blocked a Jordan Staal attempt. Bergeron stepped in front of an Alex Goligoski blast. Then Morris stuck his boot out to block a shot by Ruslan Fedotenko.

The end result: zero power-play shots for the Penguins all game.

“I thought our guys did a good job of blocking a lot of shots,’’ coach Claude Julien said after the 3-0 win. “I think we had 22 blocked shots. And they were shooting from the back end. A lot of them were our D’s. Some were forwards, but our D’s were doing a good job of fronting those. We had some big blocks, and that was important for us.’’

Fluto Shinzawa can be reached at fshinzawa@globe.com.