If you ask his teammates, the 26-year-old defenseman -- who has led the Senators to a 3-1 series lead, pushing the Bruins to the brink of elimination -- is worthy of some loftier titles.
"He's arguably the best player in the world," said Senators winger Bobby Ryan, who scored the game-winning goal in Ottawa's 1-0 victory in Game 4 on Wednesday night at TD Garden. "So you know every night he's going to break the game open somehow, whether shooting or making plays."
Boston has had no answer for Karlsson. His creativity and hockey sense is off the charts, and his speed, especially when he's closing in on the puck, has demoralized the Bruins and often left them in the dust.
Karlsson's flawless feed to Ryan -- a slap pass in front of the Bruins' net in the third period of Game 4, which set up the winner -- was the play of the night.
His teammates are quick to laud Karlsson's skill -- and his leadership. Goalie Craig Anderson has played with Karlsson for several years and Anderson gave his captain the ultimate compliment for a Senator after Game 4.
Anderson compared Karlsson to former Senators captain and future Hall of Famer Daniel Alfredsson.
"I've had the benefit of watching [Karlsson] grow as a player and a person for the last six, seven years, and what he does on and off the ice for us is unmeasurable," Anderson said. "You obviously see the points and what he does on the ice, but it's the little things that make him a great leader, a great teammate. He's starting to remind me a lot of Alfie, where guys are starting to kill themselves for him."
Karlsson has a point in every game of the series. He has five assists with 11 shots on goal, and he's averaging more than 25 minutes per game against Boston's top lines. But, as Anderson noted, many of Karlsson's contributions don't show up on the score sheet.
"He's always had that offense, that vision, that skill. But what he's done this year is use it in the right moments for the right reasons," said Ottawa coach Guy Boucher. "He's not just inspiring the guys, because he is defending so well, paying the price defensively. [He is] also managing the offensive game at the right time."
His leadership and ability to create scoring chances have inspired his teammates to step up their games.
"When you've got your top guy buying in like that, it'll translate into an entire team [following him]," said Boucher. "[Karlsson] and Dion [Phaneuf] and Kyle [Turris], those guys have done an unbelievable job of grabbing everybody and taking them in the same direction. Yeah, he's making great plays, but it's way beyond that. This guy has become something else, in every aspect."
When Karlsson was asked about his jaw-dropping ability and how he makes highlight-reel plays seemingly every game, especially in the playoffs, he simply shrugged. "It's what I get paid to do," he said with a smile, and then turned the conversation back to his team.
He and the Senators, who face Boston in a potentially decisive Game 5 on Friday at 7:30 p.m. ET in Ottawa, are one win away from moving on to the second round against either the Montreal Canadiens or the New York Rangers.
Karlsson will again be charged with shutting down Brad Marchand, the Bruins' top scorer. So far, Karlsson has thrown a wet blanket on Marchand, who scored 39 goals during the regular season but has only one in this series, the game winner in the opener. When the puck is anywhere near Marchand, Karlsson is swarming too.
"He's able to jump by everyone and be the first on the forecheck and the first on the backcheck," Marchand said. "His speed is a very special thing."
Karlsson also makes an opposing goaltender's job difficult, because he can be a force with or without the puck.
"Obviously, you have to focus on the guy who's got the puck, first of all," said Bruins goalie Tuukka Rask. "Then, recognize where [Karlsson] might be passing. He comes up with such speed that you have to be ready for everything. He's a great player and he'll make those plays. As a goalie, you just try to focus on the guy with the puck and then any opportunity there might be for a pass."
Karlsson isn't just a leading candidate for the Norris Trophy as the NHL's most outstanding defenseman, an award he's already won twice. He's also drawing Hart Trophy consideration as the league's most valuable player. But the Swede isn't focused on individual awards, especially at this time of the year.
"I play my game," he said. "I know what I have to do. I stay in the moment. I take it shift by shift -- always have and always will."
If he continues to play his game -- and impose his will -- he and the Senators will be playing deep into the spring.