"We will know more on this within a day or two as we await results of tests," Holmgren said in announcing the injury.
Hartnell saw 17:13 of ice time in the Flyers' 3-0 loss at the New Jersey Devils on Tuesday. He has one assist and 13 penalty minutes in three games this season.
The Flyers will be without Hartnell, Brayden Schenn and Zac Rinaldo for Thursday's home game against the New York Rangers. Schenn was suspended by the NHL for one game for a hit on New Jersey defenseman Anton Volchenkov in Tuesday's game, and Rinaldo is out with a lacerated right thigh.
Yeah, it was a pretty special moment for me. Today was my Dad's [55th] birthday. I have a lot of family in town, so it was a special moment for me to score my first one today. A win definitely would have capped it off, but you can't have everything.
— Sabres rookie Jack Eichel after scoring a goal in his National Hockey League debut
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