Bishop, who scored his first goal at Meadow Lane to give County the lead in Sunday's FA Cup clash with Manchester City, is struggling with a leg injury.
Fellow midfielders Lewis Gobern and John Spicer were unused substitutes in the 1-1 draw with City and will be vying to start against Walsall if Bishop fails to make it.
County manager Paul Ince has no other new injury or suspension woes, but defender Liam Chilvers remains sidelined due to a knee injury.
Striker Lee Hughes suffered no reaction in the game against City after recently returning from a calf injury and is expected to start, as is skipper Mike Edwards, who has been nursing a hamstring strain.
Walsall manager Dean Smith could recall goalkeeper Richard Walker for the trip to Meadow Lane.
Walker missed Saturday's 6-1 win over Bristol Rovers due to "family reasons", but is back in contention and could return in place of understudy David Bevan.
Defender Manny Smith is also expected to return to the squad after missing out at the weekend with a hamstring strain.
Recent loan signing Jason Price from Carlisle is hoping to retain his place up front after making his debut against Rovers, while defender Richard Taundry is pushing for a recall after returning to the bench on Saturday following an ankle injury.
Striker Darren Byfield remains sidelined with the knee injury which has kept him out since September.
The Saddlers moved off the bottom of the table at the weekend with their first league win in eight matches.
Bristol Rovers v MK Dons
Bristol Rovers manager Dave Penney could hand debuts to Gavin Williams and Jean-Paul Kalala in the home clash with MK Dons on Wednesday night.
Midfielders Williams and Kalala, both deadline day signings from Bristol City and Yeovil respectively, are hoping to play some part.
Williams is on loan until the end of the season, while Kalala has signed a short-term deal until June 30.
Penney may also play Peterborough forward Rene Howe and Reading midfielder Scott Davies after the pair joined the npower League One side on loan last week.
Rovers have no fresh injury concerns, but are blighted by suspension to two key players, with midfielder Chris Lines and defender Danny Coles both missing out.
Promising youngster Keanu Marsh-Brown could make his professional debut in MK Dons' trip to The Memorial Stadium.
The 18-year-old England youth international recently signed a new two-year contract with parent club Fulham, although he has yet to make his first-team debut.
And after penning a one-month loan deal with Dons on Monday, Marsh-Brown could make his bow in the League One clash at the Memorial Stadium.
French goalkeeper Willy Gueret, however, will not feature as he is poised to join Kettering after his Dons contract was cancelled by mutual consent.
Gueret was first-choice goalkeeper and a regular starter last season but has failed to appear for the first team this time around following the arrival of David Martin from Liverpool last July.
Midfielder Mark Carrington also plays no part having left Dons by mutual consent on Tuesday, subsequently agreeing a deal to join Scottish Premier League club Hamilton as a free agent.
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