Phantoms captain Ben Holmstrom left the game late in the second period of Saturday's shootout victory over Syracuse, appearing to favor his left leg.
According to a team source, Holmstrom's lower-body injury will likely keep him out of the lineup for an extended period of time.
Holmstrom was playing on the second line with Harry Zolnierczyk and Sean Couturier after spending much of the season on the third line with Zac Rinaldo and Rob Bordson.
The captain is one of only six Phantoms who have played in all 22 game up to this point. He has tallied eight points, two goals and six assists. He has also played on the power play; Saturday night he was the fourth forward on the first shift (used on the two five-on-three power plays) in place of Jason Akeson.