Kilgallon was forced off in the first period against Millwall at the Northern Commercials Stadium after failing awkwardly on his shoulder while making an interception.
The 33 year-old went for a scan on the injured area after the Millwall game to check for signs of any damage to the shoulder.
Thankfully for City and the defender, the checks revealed no dislocation, although Kilgallon is definitely ruled out of Tuesday's trip to Oxford United in the Checkatrade Trophy.
McCall said: "We are hopeful that it is decent news for Killa (Matthew Kilgallon) because he had two x-rays on Saturday and they didn't show any dislocation.
"That is clearly good news as it would probably have ruled him out for the season if he'd needed an operation.
"He is still in a lot of discomfort with the shoulder but he says he is a quick healer.
"He is certainly out of Tuesday night (vs Oxford) and a massive doubt for Saturday (vs Oldham Athletic).
"Whether it is days or weeks out for him, we just don't know quite yet.
"The news with the scan was positive though, so hopefully he won't be out for as long as first feared."
After two recent substitute appearances, Billy Clarke is set to make his first start since returning from injury in Tuesday's cup tie at Oxford.
Alex Jones and Alex Gilliead are once again cup-tied, however, while Tony McMahon is suspended after picking up his second booking of the competition during the win over Cheltenham Town in the last round.
McCall added: "Billy will start on Tuesday.
"We are looking to get him back in our starting XI.
"He has been looking sharp in training recently and he is desperate to get his season back up and running again.
"He was playing really well before his injury - hopefully he can regain that form and get back to playing to his best in the second half of the season."