Rakell made it 2-0 at 2:02, tapping in a backhand pass from Rust just above the crease.
Morgan Barron cut it to 2-1 at 3:50, when his shot off a rebound from Lambert was blocked by Karlsson and fluttered in as both he and Karlsson slid into Silovs. It was upheld after the Penguins challenged for goalie interference.
“(Karlsson) is part of my equation, in my head,” Barron said. “But I’m not really thinking about him. Watching it over, I kind of felt like he wedged himself in between, and I think if he’s not there, I stop and I’m nowhere near the goalie.”
Cole Koepke tied it 2-2 with a short-handed goal at 6:10 of the second period, going forehand to backhand off a pass from Adam Lowry on a 2-on-1.
Karlsson put Pittsburgh back in front 3-2 at 15:22 with a shot through traffic from the right face-off circle.
“(Karlsson) has taken it to another level, he really has,” Penguins coach Dan Muse said. “It’s been incredible to watch. ... You get to this time of the year, everything’s elevated. He’s been great all year. When it’s getting harder and it’s getting tighter, he just keeps finding a way to elevate his game.”