Sitting in the penalty box Sunday night with his Ottawa Senators down a goal and staring at a potential 0-3 deficit in the Eastern Conference Semifinals against the Pittsburgh Penguins, Karlsson was not thinking happy thoughts.
"I don't know," the defenseman said when asked to describe his frame of mind after being called for slashing with 1:27 to play in regulation of Game 3 Sunday. "It's not looking bright."
But Senators captain Daniel Alfredsson scored a shorthanded goal with 28.6 seconds left to tie the game, and Colin Greening scored in the second overtime to give the Senators an unlikely win, thus ensuring Karlsson's outstanding performance was not overshadowed by his penalty at the end of a one-goal game.
Ottawa trails the best-of-7 series 2-1 with Game 4 Wednesday at Scotiabank Place (7:30 p.m. ET; NBCSN, CBC, RDS).
After struggling in Game 1 at Pittsburgh, Karlsson was limited to 15:37 of ice time by coach Paul MacLean in Game 2.
MacLean justified that decision by saying the players playing the best will see the most ice time.
In that case, Karlsson should be pretty happy with himself about what he did in Game 3.
He played a game-high 39:48, with the great majority of his 41 shifts coming against Sidney Crosby, Chris Kunitz and Pascal Dupuis, helping to limit that trio to eight shots on goal combined.
"I thought Erik Karlsson played an excellent game," MacLean said. "I thought he responded after the game in Pittsburgh and really came out and played."
Karlsson mentioned after his difficult games in Pittsburgh that he needed to mentally adjust to his abilities after coming back from a lacerated Achilles tendon, noting his need to trust what he is doing on the ice.
He did that Sunday, showing great assertiveness and combining with partner Marc Methot to form a very effective shutdown pairing.
"I think I just need to go back to what feels normal," Karlsson said. "I can't think too much about what happened in the past. I just need to play the way I've always been playing, even if it doesn't work out all the time. I've got to make a decision and stick to it even if it doesn't turn out to the right one.
"Today it turned out OK."
It actually turned out considerably better than that.