He is expected to be re-evaluated on Friday.
"It's frustrating, obviously," teammate Scott Hartnell said. "He was finally getting his timing back from his concussion, and I'm sure he'll be out four to six weeks, I'm guessing. . . . But the blessing in disguise is he'll be well-rested and ready to go come playoff time."
van Riemsdyk, who signed a six-year, $25.5 million contract in the summer, has collected 11 goals and 13 assists for 24 points in 43 games this season and was reportedly on the trading block before his concussion.
Flyers GM Paul Holmgren told reporters earlier this week that the young winger received interest from more than a few teams, though he says the Flyers never had an interest in moving him.