OTTAWA -- Before the Boston Bruins can even think about a comeback unlike any the franchise has managed before, they have to figure out a way to stop Erik Karlsson.

The quarterback of the Ottawa Senators' attack is killing them with his passing.

Karlsson, clearly the best player in the best-of-seven, first-round Eastern Conference playoff series the Senators lead 3-1, is tied for the series scoring lead entering Game 5 at Canadian Tire Centre on Friday. All five of his points have been assists, while three have been of the spectacular variety and led to wins.

His most recent work, a third-period slap pass to Bobby Ryan on Wednesday, set up the lone goal in a 1-0 Senators victory.

In Game 3, Karlsson made a 140-foot saucer pass to Mike Hoffman for a breakaway goal that was the game's first, and in Game 2 he made a magnificent cross-grain pass through the slot to Derick Brassard to start a third-period rally.

"Again, 65 looks like the best player in the world right now," Senators winger Mark Stone told Postmedia, referring to Karlsson's jersey number. "Again, he makes the big plays for us."

Ahead of Game 5, the Bruins are in a serious jam. In their 92-year history, they have played 96 best-of-sevens, and never before in 22 tries have they rebounded from a 3-1 deficit to win the series.

The Bruins have also lost nine of the past 10 games they have played against the Senators dating back to last season.

"As a whole, our team has to have second-chance opportunities," Bruins coach Bruce Cassidy, whose team has yet to outshoot the Senators in any of the four games, told the Boston Globe. "We're lacking in that area, and it starts with our shot total. It's on us to hit the net and get some second chances. Let's shoot for rebounds from off angles, hit the net first and get people there."

While the Bruins did get defenseman Colin Miller back from the injury list Wednesday, blue-liners Torey Krug, Brandon Carlo and Adam McQuaid are expected to remain sidelined for Game 5.

There is also some question as to the availability of winger Frank Vatrano, who was spotted leaving TD Garden in a walking boot Thursday.

Ottawa will likely be without winger Tom Pyatt, who was knocked out of Game 4 with a high hard hit by Kevan Miller early in the first period.

The Senators, who have only won one of six playoff series since going to the Cup final in 2007, have never lost a 3-1 series lead. Coach Guy Boucher said he "couldn't care less about history," and that the focus is only on a good start in Game 5.

"We can't look at it as 3-1," Boucher said. "That's exactly what we don't want to do. It's those first 10 minutes of the next game that need to be a strong 10 minutes, and they we'll manage the rest. That has been the approach since training camp, and it has to continue to be our approach."