"We're struggling right now," Karlsson said. "You're going to go through periods of this throughout the year. We're going through it right now and we're going to have to sort a lot of things out."
Karlsson played 24:55 and had nine shots on goal.
"I think we're disappointed for Erik," Sharks coach Pete DeBoer said. "I think we're disappointed for ourselves. This was a big game for us. We wanted to bounce back after losing [at the Toronto Maple Leafs 5-3 Wednesday], and the game ran away from us."
Anderson made 27 saves in a 3-0 win against the New York Rangers on Thursday.
"We've seen ourselves grow in the last two games," Anderson said. "The last game against the Rangers, we were outstanding for 60, and tonight again, outstanding for 60 minutes. We're starting to string some momentum together, and playing in the right direction, playing the right way, and I think our guys are getting rewarded too, we scored [six] goals."
Ryan Dzingel gave the Senators a 1-0 lead at 7:30 of the second period. Ben Harpur scored his first NHL goal to make it 2-1 at 12:56, and Boedker scored on a breakaway to make it 3-1 49 seconds later.