Forward Bryan Rust also didn't practice. He was still being evaluated Sunday after blocking a shot by Sabres defenseman Colin Miller with his hand, Sullivan said.
Forward Alex Galchenyuk, who did not play the Penguins' final two preseason games because of a lower-body issue, remains day to day. He had an off-ice workout Sunday and is expected to skate with skills coach Ty Hennes when the Penguins have a day off Monday.
If Crosby, Rust and Galchenyuk are unable to play Thursday, Pittsburgh could start the season without three of its top-six forwards.
"I think we have four more days for [them to get back]," center Evgeni Malkin said. "I hope it's not bad. It's always tough if we lose a couple of good players. It's like we know, [Crosby] and Rust, they're a huge part of [the team]. We just need to wait and see what's going on. I hope they're back. But we still have four lines. We play if they're not back."
Crosby played his first preseason game Wednesday, when he scored a third-period goal against the Detroit Red Wings, after being held out of the first four games. Immediately after practicing in Cranberry, Pennsylvania, on Friday, Crosby traveled to Rimouski, Quebec, to attend a ceremony where the Quebec Major Junior Hockey League retired his No. 87. He returned Pittsburgh in time to play his second preseason game Saturday.
Crosby has played 161 of the Penguins' 164 games the past two seasons, including 82 in 2017-18, the only time he's played a full 82 games in 14 NHL seasons. In 79 games last season, Crosby reached 100 points (35 goals, 65 assists) for the first time since 2013-14, when he had 104 (36 goals, 68 assists). He was primarily paired with Guentzel, who scored 40 goals with Crosby assisting on 25 of them.
"I'm not really sure what's going on either, but if you lose a player like that, I think it's got to be by committee," Guentzel said. "He's such a good player and does everything for us."