The Capitals defenseman was penalized for interference at 4:13 after hitting Maatta in Washington's zone. Maatta needed assistance to leave the ice and was helped to the locker room.
"He's obviously out," Penguins coach Mike Sullivan said after a 2-1 win. "We'll have more details probably [Sunday] on his status."
The best-of-7-series is tied 1-1 with Game 3 at Consol Energy Center on Monday (8 p.m. ET; NBCSN, CBC, TVA Sports).
