Evgeni Malkin replaced Crosby at first-line center with Jake Guentzel at left wing and Bryan Rust at right wing.
Pittsburgh was 46-25-11, third in the Metropolitan Division, despite playing a chunk of this season without Crosby and Malkin. But it was 5-4-4 in 13 games without Crosby.
The 34-year-old missed the first seven games after having offseason wrist surgery before returning Oct. 30 and missing the ensuing five in NHL COVID-19 protocol. Crosby did not play in a 3-0 loss at the Rangers on April 7 because of a non-COVID illness.
Malkin had knee surgery June 4 that kept him out until Jan. 11, when the Penguins were 20-9-5. He had three points (two goals, one assist) in his return in a 4-1 win at the Anaheim Ducks.
"It should just give us confidence that we can win games regardless of who's in our lineup," Sullivan said. "We have a lot of depth at a lot of positions and we believe we have what it takes to win. We've got a capable group. This group has always had the next-man-up mentality. We'll continue to do that moving forward here."
Crosby leads Pittsburgh with nine points (two goals, seven assists) this series after scoring six (three goals, three assists) in 14 playoff games the previous three seasons. He had one goal and two assists in Game 4, a 7-2 win, to become the sixth player in NHL history to reach 200 playoff points (71 goals, 129 assists).
The line of Crosby with Guentzel and Rust has scored 10 of Pittsburgh's 23 goals in the series.
Guentzel has scored seven goals, tied with Minnesota Wild forward Kirill Kaprizov for the most in the playoffs. Crosby assisted on the first five.
"We're not going to get ahead of ourselves," Sullivan said. "We're going to take each day as it comes here. But regardless of what our lineup looks like, each and every night, we believe we have what it takes to win."
Crosby scored 84 points (31 goals, 53 assists) in 69 games during the regular season, tied with Guentzel for the most on the Penguins. He scored his 500th NHL goal Feb. 15 and reached 1,400 points in his 1,100th game, a 3-2 overtime win against the Nashville Predators on April 10.
The Penguins are confident but also realize there is no replacing what Crosby brings this time of year, with him having won the Stanley Cup three times (2009, 2016, 2017).
"He's a great leader. He's the standard," Sullivan said. "He personifies what it means to be a Pittsburgh Penguin. So he's not only a leader through his actions, but he's a leader through his demeanor and how he carries himself. He's a voice of reason through an emotional, turbulent game.
"So that's what he brings to our team. He's just a great leader, both on the ice and off the ice. I'm probably stating the obvious, but he means a lot to this organization. He means a lot to this team."
