Michael Raffl has been one of the Flyers better play-drivers and made the fourth line effective over the early portion of the season. He's also been a bright spot on an otherwise dismal penalty kill.

But on Monday night, Raffl left the game in the second period, unable to put any weight on his left leg. The prognosis the day after the Flyers 4-1 loss to Colorado wasn't shocking. Raffl will be out for four-to-six weeks with a lower-body injury, GM Ron Hextall announced on Tuesday.

Raffl had two assists in the first nine games of the season, averaging 12:15 of ice time. Raffl is in his sixth season with the Flyers.

The injury opens the door for either Mikhail Vorobyev or Corban Knight to rejoin the lineup. Knight played in Raffl's spot in practice on Tuesday. Vorobyev took a spot on the third line again, but both Claude Giroux and Nolan Patrick did not participate in the practice, leaving question as to who factors into the lineup.

The Flyers continue the season on Thursday night with a trip to face the Boston Bruins. Game time is at 7 p.m.

Kevin Durso is Flyers insider for 97.3 ESPN and Flyers editor for SportsTalkPhilly.com. Follow him on Twitter @Kevin_Durso.