Whing (ankle) and Smalley (groin) were taken off during Saturday's 3-1 victory over Mansfield and will miss the trip.
The U's midweek FA Cup replay at Gateshead was postponed because of a waterlogged pitch after Chris Wilder's men made the 500-mile round trip.
The 25-year-old missed the 2-1 defeat to Rochdale after twisting his ankle in the Southend clash the previous weekend. He looks likely to play some part against the Sky Bet League Two leaders.
Jack Redshaw, who returned from his long-term hip injury against Burton at the beginning of the month but has since had further injury problems, is nearing full fitness.
Defender Chris Doyle could come into Bentley's first-team plans following a spell on the sidelines with a knee injury.
- Sports & Recreation
- Dave Kitson
- Alfie Potter
- James Constable
- Jim Bentley
- Chris Wilder
- Andy Parrish