Former Addicks right-back Richardson missed the defeat by Brentford last time out with a thigh injury and midfielder Chaplow has been struggling with an Achilles problem.
Defender Jose Fonte returns from a suspension and should come straight back into the side with Dan Seaborne the most likely to make way.
Rickie Lambert was a slight doubt for last week's trip to Walsall with a dead leg, but after that match was postponed he is now fine.
However, fellow striker Lee Barnard is expected to miss out again with an ongoing groin problem.
Winger Lee Holmes is a long-term absentee with an ankle injury.
Source: PA
Source: PA