Karlsson revealed after Ottawa advanced past the Boston Bruins in the first round that he sustained the injury blocking a shot late in the regular season. In the postseason, he played after having his foot frozen and being injected with painkillers.
It's going to take awhile for Karlsson and the Senators to get over their loss to the Penguins.
"It obviously stings, but at the same time it happened for a reason," Karlsson said. "We moved in the right direction. We're happy where we ended up even though you're not satisfied."
"Both days you wake up, it hurts," forward Clarke MacArthur said. "You're so close to having a chance of doing something great. It just shows you how hard it really is."
MacArthur, who sustained a concussion in training camp and briefly retired after Christmas, returned to play the final four regular-season games and had nine points (three goals, six assists) in the playoffs. He did not commit to returning next season, saying he played with a sore neck after the first round and wants to confer with doctors before deciding on his future.
After they exceeded predictions by the experts, the Senators said they will use the loss to the Penguins as motivation during the offseason.
"This is one of those ones that stings for a little while," said forward Bobby Ryan, who had 15 points in 19 playoff games after he had 25 in 62 regular-season games. "Eventually you'll look back at it and use it as a motivational tool and a learning thing.