he Scotland goalkeeper was sent off at Rotherham last weekend for kicking out at Millers striker Matt Derbyshire. He had his three-match ban reduced to two games on appeal in midweek.
Simon Moore, who started the first two league games when Marshall was suspended at the start of the season, will deputise again.
Striker Kenwyne Jones could return to the starting line-up after being rested to the bench for the 2-1 defeat at Rotherham, with loan signing Sammy Ameobi expected to drop out.
Charlton are struggling with injuries and suspension ahead of the trip to south Wales.
Goalkeeper Stephen Henderson, midfielder Christian Ceballos and forwards Igor Vetokele, Simon Makienok and Reza Ghoochannejhad are all still sidelined and were this week joined by club captain Johnnie Jackson, who was injured in training.
Former France international Alou Diarra will also be missing as he is banned following a red card in the 4-1 Capital One Cup defeat at local rivals Crystal Palace on Wednesday.
Ahmed Kashi, Patrick Bauer, Johann Berg Gudmundsson and Tony Watt should return after starting on the bench at Selhurst Park, with boss Guy Luzon desperate to avoid more first-team players picking up injuries.
