Rust, Hornqvist and Schultz are recovering from upper-body injures. Kuhnhackl has a lower-body injury.
\[RELATED: Complete Penguins vs. Senators series coverage\]
With the best-of-7 series tied 2-2, any reinforcements would be helpful. If Schultz is able to play Sunday, his return would be timely because defenseman Chad Ruhwedel sustained a concussion on a hit from Senators right wing Bobby Ryan with 25.6 seconds remaining in the first period of the Penguins' 3-2 win in Game 4 on Friday.
"It's a possibility," Sullivan said of Schultz playing on Sunday. "His status is day to day."
If Schultz is unable to play, Mark Streit, who played when the Penguins dressed seven defensemen in a 5-1 loss in Game 3 on Wednesday, will be the leading candidate to replace Ruhwedel.
The Penguins have dressed a patchwork defense throughout the Stanley Cup Playoffs, with Kris Letang sidelined for the rest of the season following neck surgery and others going in and out of the lineup with injuries. Trevor Daley missed four games with a lower-body injury but returned for Game 3 against the Senators after Schultz was injured on a hit from Mike Hoffman in Game 2.
Despite the injuries, the Penguins have survived on defense and got an offensive bonus in Game 4 when defensemen Olli Maatta and Brian Dumoulin scored goals.
"We're not a perfect group back there by any stretch, but these guys are playing hard and I love their commitment level," Sullivan said. "We've had so many games over the course of this playoffs where we've lost a defenseman early in the game and were forced to go to five and these guys they don't think twice. They just keep playing and nothing fazes them back there. I've said a lot that they're the unsung heroes of this team."
