Line changes working for Penguins, Flyers

Five things we've learned from Thursday:

1. Philadelphia's coach John Stevens has raised the possibility that his two top defensemen, Braydon Coburn and Kimmo Timonen, missing for most of the series, could make a return at some point.

"Well, we won't know until each day … but is there a chance? I think there is, either or both," Stevens said after Thursday's Game 4. "The first thing is you have to make sure of is the health of the player here, and we're not going to put anybody at risk. If they're not able to go, we'll keep marching ahead like we are. But if we're able to get one or both back, it would be a huge lift for our team."

It was thought that Timonen would be lost for the balance of the season with a blood clot in his ankle, while Coburn took a Hal Gill shot to the face early in Game 1 and hasn't felt well enough to play. The return of one, or both, of the skilled rearguards would be a huge boost to a Flyers team that has struggled to move the puck through the neutral zone.

2. On the Penguins' side of the infirmary, veteran forward Gary Roberts remained out of the lineup for Game 4 with what the Penguins were calling a mild case of pneumonia.

"He's still sick. He's got pneumonia," Penguins' coach Michel Therrien said before Game 4. "It's a mild case, so he's listed day-to-day. He's not going to play tonight."

Asked if Roberts was expected back later in the postseason, Therrien was noncommittal. "Yes, yes, hopefully. He's on medication right now, and we'll go from there."

3. Pittsburgh's center Jordan Staal returned to the lineup after spending all day Wednesday jetting to and from his grandfather's funeral in Thunder Bay, Ontario, and scored twice in a losing cause. Landlord and former teammate Mark Recchi helped arrange a charter jet so Staal could be with his grieving family and return for Game 4.

"He's an unbelievable guy," said Staal, who still lives at the Recchi family compound in Pittsburgh after Recchi was traded to Atlanta. "He helped me out so much throughout my career, such a great friend to me. He and his family have been unbelievable."

The visit home was difficult. "I don't know if you lost anyone close, but it wasn't easy," Staal said. "My opa was real close to my whole family, especially all his grandchildren. He's an amazing man and I miss him."

4. Midway through the second period of Game 4, Philadelphia defenseman Randy Jones drilled Pittsburgh's Evgeni Malkin headfirst into the boards behind the Flyers' net. Malkin jumped right up and continued his shift, but we're wondering how a play like that goes unpenalized? This is the same Randy Jones, by the way, that ended Boston star Patrice Bergeron's season early in the campaign with a hit from behind that wasn't all that much different from what we saw Thursday night in Philadelphia.

5. Both coaches went to a different look with their line combinations Thursday and both were successful. Stevens moved Mike Richards onto a line with Daniel Briere and Scott Hartnell, dropping Vaclav Prospal back to a line with R.J. Umberger and Joffrey Lupul. Lupul scored the Flyers' first goal. Therrien, meanwhile, moved Max Talbot onto the wing with Staal and Tyler Kennedy. The line scored both Penguins goals in the third period with each linemate recording two points.

Scott Burnside is the NHL writer for ESPN.com.