Instead, Karlsson faced trade speculation last offseason as part of a potential Penguins rebuild that never materialized. He stayed and was named team MVP with 66 points (15 goals, 51 assists) in 75 games.
Karlsson now could be key to Pittsburgh winning its first postseason series since defeating Philadelphia in the 2018 first round.
"Obviously, [the playoffs are] why I came here to begin with," Karlsson said. "I believe in this group. From an outside perspective, and being here now for three years, the potential has always been there."
Karlsson knows the Penguins. They've arguably been his biggest roadblock.
Pittsburgh took five games to eliminate Karlsson and the Ottawa Senators in the 2013 Eastern Conference Second Round. On May 25, 2017, Chris Kunitz scored 5:09 into the second overtime of a 3-2 win against Karlsson and Ottawa in Game 7 of the Eastern Conference Final.
Crosby, Malkin and Letang led the Penguins then, and still do now.
"I mean, it's been brutal for me playing against those guys over the course of my career," Karlsson said. "I never had any real success, so it's going to be nice to have them on your side."
The feeling is mutual.
"[Karlsson is] just somebody that I felt like always elevated," Crosby said. "As good as he is, he always found another level in the playoffs. That's something that, from playing against him, you understood that. You knew that he had the ability to make an incredible play that could change the game.
"It's way better having him on our team. I've seen what he's capable of and what he can do, and he's been doing it all year."
Karlsson has embraced a standard set by Crosby, Malkin and Letang. At 20 seasons together, they are the longest-tenured trio of teammates in North American professional sports.
"I think with 'Tanger' and 'Geno,' every single night we play, I know that they want to win," Crosby said. "It's not something you really have to talk about."
Each season, they intend to play into late-April, May and even June. That expectation was dented by the three-year drought, but never fully went away.
"It's been hard. We don't know anything but [making the playoffs]," Letang said. "It was a shock. Obviously, disappointing. But now, we're here today and we're excited."