Giroux sustained an unspecified lower-body injury during Monday's practice and missed Tuesday's practice.
"I can't give a definitive time line, but I don't expect it to be long," Hextall told reporters, regarding how long Giroux will be out.
The injury will snap a streak of 146 consecutive regular-season games played for the Flyers captain, who is tied for seventh in the NHL with 21 points. All five of his goals this season have come on the power play, tied for the most in the NHL.
Giroux, 27, was the 22nd overall pick by the Flyers in 2006 from Gatineau in the Quebec Major Junior Hockey League. He scored 28 goals and notched 86 points last season, finishing as a finalist for the Hart Trophy.
The Flyers (7-7-2) will head to Madison Square Garden Wednesday night, where they have lost eight straight regular season games to the New York Rangers (7-7-4).
- Phil Watson