Hertl opened the scoring just 1:16 in when the puck bounced over the stick of Senators defenseman Joe Corvo, allowing Hertl to quickly put a shot between Anderson's legs.
Just over five minutes later, sloppy play by the Senators in their end allowed Desjardins to make it 2-0. He picked up a rebound and scored off his backhand.
"I just thought we chased the game the whole night," Ottawa coach Paul MacLean said. "I'm very concerned about the way that we've played to this point in the season."
Ottawa cut the lead in half midway through the period when Karlsson scored through traffic. With forward Cory Conacher creating a screen, Stalock barely had a chance to see the shot until it was behind him.
Any momentum gained from the goal was lost after the Senators gave up a short-handed goal with less than two minutes remaining in the period.
"Our identity in the past has been a hard-working group that's very competitive and comes to play the whole game and plays hard the whole game," MacLean said. "Right now we don't do that. So what is our identity?"
Karlsson bobbled the puck at his blue line, and Logan Couture took off on a breakaway. Anderson made the initial save, but the puck rested in the crease. Wingels banged it in to restore the two-goal lead.
"Right now, we make a mistake and it ends up in our net," Anderson said. "I'm not sure how you change that. You need a little bit of luck, but at the same time you've got to limit the amount of mistakes you make."
NOTES: Ottawa LW Clarke MacArthur missed the game with what the Senators described as a minor injury. LW Matt Kassian and D Eric Gryba were healthy scratches. ... San Jose is still without RW Brent Burns, who was struck in the mouth by a puck. RW Marty Havlat sat out because of a pelvis injury, and D Dan Boyle missed his sixth straight game. LW Matthew Nieto was a healthy scratch.
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