Head coach Bruce Cassidy said Monday that Marner is dealing with an illness, Danny Webster of the Las Vegas Review-Journal reports.
Following Sunday's 5-0 loss in Pittsburgh, the Golden Knights have an illness going around the room, which includes Marner, Shea Theodore and another unnamed player. The 28-year-old Marner should be considered questionable for Tuesday's road matchup against the Sabres. Alexander Holtz would more than likely draw into the lineup if Marner can't suit up in Buffalo.