Cernak, a defenseman, was injured at 15:40 of the second period of the Lightning's 7-3 win in Game 1 of the best-of-7 series on Tuesday when he was hit by Maple Leafs forward Michael Bunting.
Bunting was assessed a five-minute match penalty for an illegal check to the head and was scheduled to have a hearing with the NHL Department of Player Safety on Wednesday.
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Hedman, also a defenseman, left after the first period of Game 1 because of an undisclosed injury.
Lightning coach Jon Cooper said Tampa Bay's mindset would not change if key players were unable to be in the lineup for Game 2.
"It would be easy to sit back and say, 'Oh, we got the first one,' " Cooper said Wednesday. "We got the first one last year and it's easy to go back with that. See, I don't agree with that. It's like, let's go be greedy and put the pressure on them."
Zach Bogosian, who played in three of the Lightning's final nine regular-season games, could enter the lineup in place of Cernak. If Hedman can't play, a spot would open for Haydn Fleury, who played in three of Tampa Bay's final 17 games during the regular season.
Forward Michael Eyssimont also is out for Game 2; he left Game 1 after taking a hit from Toronto defenseman Jake McCabe at 13:45 of the second period.
Forward Tanner Jeannot will be a game-time decision after missing four games, including Game 1, because of a lower-body injury.
"I feel good, but there's a lot of things that go into it," Jeannot said.
NHL.com staff writer Mike Zeisberger contributed to this report
