The Boston Bruins found answers to their slow start after 20 minutes, while the Ottawa Senators were left questioning their lack of effort over the final 40.
The Bruins and Senators now head north to conclude a home-and-home set Saturday night in Ottawa.
On the heels of a 5-0 thumping of Pittsburgh on Monday, Ottawa (15-18-7) showed plenty of jump in the first period at Boston on Friday night, outshooting the reigning Eastern Conference champions 15-5 but failing to beat Tuukka Rask in a scoreless first period.
The Bruins (26-10-2) then responded as champions do - by taking over the game.
Jarome Iginla netted a power-play goal late in the second to snap the scoreless deadlock, and Reilly Smith had two of the team's four third-period goals to complete a 5-0 romp, giving the Bruins eighth straight home wins and extending their point streak there to 15 games (13-0-2).
Smith, who came over from Dallas in the offseason as part of the Tyler Seguin deal, has five goals and two assists in his last three games and leads the team with 14 goals.
"I don't think he was looked upon as a throw-in," Bruins coach Claude Julien said of the 22-year-old Smith. "It is the first time he has been given the opportunity to play on a regular basis, and he is finally showcasing his skills. It's no fluke."
Reilly, who has six goals and nine assists in 17 road games, was held off the scoresheet in Boston's 4-2 loss at Ottawa on Nov. 15.
Rask, who finished with 33 saves, improved to 5-2-0 with two shutouts and a 1.84 goals-against average versus Ottawa.
For the Senators (15-18-7), their rollercoaster season of inconsistency continued as they absorbed their second five-goal loss this season. Ottawa, which has won consecutive games only twice, has dropped five of seven overall (1-5-1) and will try to regroup and win back-to-back home games for the first time since Dec. 9 and 12.
"They'll do the same thing to us tomorrow if we play the same way," center and captain Jason Spezza said. "We better bring a better effort, they're an elite team.
"The last two periods we gave them all their chances, so we get too passive in the second two periods and make mistakes and give them chances and that's been the calling card of our team all year."
It's likely Craig Anderson - who turned aside 27 shots in Monday's win over the Penguins - will be back in net after Lehner faced 37 shots over the final two periods. Anderson had 32 saves in last month's win over the Bruins, ending a personal five-game losing streak to them and improving to 4-8-0 lifetime.
Despite having one goal and six assists in his last five games, defenseman Erik Karlsson has a minus-4 rating in that span.
Bruins defenseman Dennis Seidenberg will not make the trip with the team after suffering a lower-body injury in Friday night's win.