Striker Anton Forrester could be missing for up to three months after the player broke down for the second time on returning to the Vale line-up.
Forrester injured his hamstring for the third time this season and left the field just 40 minutes into the game against Oldham.
The forward first injured his hamstring against Bury in September, was injured on his comeback game against Coventry in October and was injured again on Tuesday evening.
Manager Bruno Ribeiro commented: “It is three times the same. I don’t know now how long, maybe two to three months. We will go and see because this is the third time. It is difficult but we will go and see how long.”