Derick Brassard, Colin White and Matt Duchene scored, and Craig Anderson made 17 saves for Ottawa (19-27-9), which has given up six goals in consecutive games.
"We played well," Duchene said. "Murray was good early for them and we were outshooting them (by a) 2-1 (ratio) going into the third period and most of the third period too. So, it's tough when you get a few bad bounces and some really nice plays by them. They're one of the top teams in the League for a reason. They're back-to-back champs for a reason.
"They have some of the best players in the League on their team. So, there are a lot of good things, but obviously, in a loss, there are always things you can learn from and clean up."
Guentzel scored on the power play at 4:07 of the first period to make it 1-0. Justin Schultz saved the puck from being cleared twice at the blue line before taking a slap shot that Guentzel deflected past Mike Condon.
Brassard tied it 1-1 at 4:18 of the second period. Mark Stone passed to Brassard, who scored under Murray's arm with a slap shot from the left circle.