"You just feel bad for him," defenseman Jack Johnson said. "He's had a great year. He's been a big part of our team. The way he went off (the ice), I knew it wasn't going to be good. I was just hoping it wasn't going to be that bad."
Guentzel injured his right shoulder when he fell awkwardly into the boards after getting entangled with Ottawa defenseman Thomas Chabot after scoring his 20th goal of the season during the third period of Monday night's 5-2 win over the Senators - after earning his first-ever All-Star nomination earlier in the day.
"I think the overall play in general was a fluky one," Rust said. "I think skates collided at probably the worst possible time at the worst distance from the boards. It was kind of a brutal collision. I had front-row seats to it and I was definitely worried when it happened, but to see him get up from it and walk off the ice was good."
This is the first major injury of Guentzel's young NHL career. Since being called up to Pittsburgh on a permanent basis midway through the 2016-17 season, the 25-year-old forward had not missed a game until now.
During that time, Guentzel established himself as a core player on the team and one of its best and most consistent offensive performers, particularly in the goal-scoring department.
"His play speaks for itself," Penguins head coach Mike Sullivan said. "He's been one of our more consistent players here for a long time. And he's a tough kid. He's quietly become one of the elite players in the league. I know his teammates, his coaching staff, his management team all appreciate what he brings to this team. He's not an easy guy to replace. But we've lost some tough guys to replace throughout the course of this whole season. I know we have the wherewithal to continue to try to find ways to win."
In a season where Pittsburgh was plagued by 152 man-games lost due to injury (including stretches of 10+ games without key players such as Rust, Evgeni Malkin, Patric Hornqvist, Brian Dumoulin, Justin Schultz and of course, Sidney Crosby, Guentzel had been the constant in helping the Penguins to the fifth-best record in the league.
He certainly stepped up in a big way, but now, his teammates are going to have to do their best to, as Rust put it, "pick up the slack by committee."
"It's something that we've been doing all year," Rust said.
What has helped them find success doing that all year, the Penguins said, is the system that the coaches have put in place for them. Sullivan said a lot of it boils down to commitment, attention to detail and a willingness to play the game a certain way. Everybody has bought in, and they're getting results because of it.
"Coach gives us everything for how we need to play in the D zone, in the neutral zone," Malkin said. "We just play right. If you play right, if you play hard, you score goals."
While the Penguins will continue doing that, they are also keeping in the back of their minds that their other injured players are making progress.
"You look ahead and you know you're going to get guys back," defenseman Kris Letang said. "We just want to keep playing and playing well until a couple bodies come back."
One of those players was Crosby, who took the ice with his teammates for the first time on Tuesday afternoon at UPMC Lemieux Sports Complex since having surgery to repair a core muscle injury on Nov. 14. To see him out there for the first time in seven weeks was a welcome sight.
"The timing of him joining us, I think, was appropriate for the group," Sullivan said. "I know our guys certainly get excited when he's on the ice."
While Crosby - who wore a white "no contact" jersey - only joined the practice session because it was the only available ice time for him to skate (get the full update here), it was still a big boost for his teammates to have him out there today.
"It's awesome," Rust said. "You could see that smile on his face today. He was jumping around. He was excited to be out there. That's always a really good sign. He's our captain, he's one of the best players in the world, if not the best player. So that'll be good to have him getting closer."
In the meantime, the Penguins' focus is on hosting San Jose Thursday night at PPG Paints Arena.
"We're taking a very short-sighted approach with this group right now," Sullivan said. "We're looking at one game and that's the San Jose game and the group of healthy players that we have. We'll try to put combinations together to win that game."