On-loan Bournemouth centre-back Zubar sustained a knee problem against Notts County on Friday and is awaiting the results of a Monday afternoon scan.
The 26-year-old departed at half-time and his absence was keenly felt as the Shakers' saw a 1-0 advantage spiral into a 4-1 defeat, a third consecutive loss that leaves Kevin Blackwell's side eight point from safety having won only once in their past 14 league matches.
To make matters worse, Blackwell is operating under a transfer embargo for the second time since taking charge at Gigg Lane last September.
He told BBC Radio Manchester: "It's just been a catalogue of poor decisions that have been made that have left the club where it is. You're then having to try and solve it all the time. It makes it difficult.
"We've got what we've got now - we can't change anything with players. Unless someone comes in and gives us the money and gets us out of the embargo, we can't do anything there."
Defenders Phil Picken (knee) and Adam Lockwood (groin) remain on the sidelines along with midfielder Shane Byrne (blood disorder).