The on-loan striker was recalled by parent club Coventry on Monday, just days after netting the only goal of the game to clinch three points at Chesterfield.
Deon Burton and Adam Birchall are now the leading contenders to step in for McDonald, while 12-goal Danny Kedwell is not too far off his comeback from a hamstring injury, although a start against the U's is likely to be a step too far.
Right-back Matt Fish will be assessed having been forced off at the Proact Stadium with a twisted ankle.
Andy Frampton missed the game altogether due to concussion and he continues to be monitored, while fellow midfielder Charlie Allen (wrist) is not yet ready for action.
- Sports & Recreation
- Adam Birchall
- Deon Burton