"I know how they play and I know what to do," Karlsson said.
Hertl missed Game 3 with a lower-body injury, and he did not go on the ice for San Jose's optional skate Sunday. DeBoer said Hertl is still "day-to-day. It's likely that Karlsson will skate on the top line again in Game 4 on Monday in San Jose (8 p.m. ET; NBC, CBC, TVA Sports).
"Melker, like the rest of our group, was great," DeBoer said. "He was tenacious, on the puck. He was in on the forecheck, caused the turnover on the overtime goal. We talk about interchangeable parts, but we have a lot of guys that play on our third line, play on our fourth line, that can jump up or have played higher in the lineup in the past.
"I think when you have really good players up top, you can have those interchangeable parts. Pittsburgh has got it. You look at the guys they pair with [Evgeni] Malkin or [Sidney] Crosby. They're not household names, some of them. Because you have quality people up top, you can stick in complementary guys like that and they can be very effective. I think Melker is one of those guys."