Shanahan scored two goals and the Rangers beat the Senators 5-2 Saturday, handing the Eastern Conference champions their sixth straight loss.
With the win, the Rangers moved a game behind Ottawa for the conference lead.
"We came in here definitely catching a team down," said Shanahan. "And when a team is down you want to jump on them and you don't want to give them a chance to build confidence and build good things."
Henrik Lundqvist made 32 saves for his league-leading 14th win. Jaromir Jagr, Dan Girardi and Blair Betts also scored for New York, which took a 4-0 lead before Joe Corvo and Dany Heatley scored for Ottawa.
"I thought towards the end of the second and into the third we showed a little more energy in their zone," Senators coach John Paddock said. "We're a good hockey team that's a lot better than we're playing right now. But we're not winning lots of battles in the corners either offensively or defensively."
Girardi scored 3:37 into the game and Shanahan followed four minutes later. Jagr scored four minutes after that to put Ottawa in a 3-0 hole.
"Ottawa's having a bit of a tough stretch right now, as everybody does, and we respect that as much as anybody because we've been through that," Rangers coach Tom Renney said. "The gap's been closed by a combination of the fact that we've played better and they've been having a bit of a tough go."
|Henrik Lundqvist makes one of 32 saves to earn his league-best 14th victory. (AP)|
|NY Rangers (15-9-2) «||3||1||1||5|
Save Pct.: .939
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|03:37||Daniel Girardi (3), Slap Shot. Assist: Marcel Hossa|
|07:23||Brendan Shanahan (7), Slap Shot. Assist: Scott Gomez, Marcel Hossa|
|11:40||Power Play - Jaromir Jagr (8), Slap Shot. Assist: Michal Rozsival|
|09:33||Power Play - Brendan Shanahan (8), Slap Shot. Assist: Martin Straka|
|14:28||Joe Corvo (4), Slap Shot. Assist: Jason Spezza, Daniel Alfredsson|
|14:02||Dany Heatley (14), Slap Shot. Assist: Jason Spezza, Daniel Alfredsson|
|19:18||Blair Betts (1), Empty Net, Unassisted.|
|10:21||Spezza, 2 min, Hooking|
|14:14||McGrattan, 2 min, Unsportsmanlike Conduct|
|17:17||Straka, 2 min, Holding|
|33.0||Tyutin, 2 min, Roughing|
|01:48||Spezza, 2 min, Tripping|
|08:46||Vermette, 2 min, Hooking|
|15:20||Fisher, 2 min, Tripping|
|07:16||Corvo, 2 min, Holding|
|15:09||Prucha, 2 min, High-Sticking|
|Shots On Goal|
|Attendance - 20003|
|Referees - Tim Peel, Brian Pochmara|
|Linesmen - Steve Miller, Greg Devorski|