Richardson suffered a recurrence of his hamstring problem during last weekend’s win over Southend and fellow defender Youga is struggling with a knee injury.
Striker McLeod has also picked up a knock to the knee and is another doubt.
But midfielder Jose Semedo returns from a one-match ban and forward Leon McKenzie is available after overcoming his knee injury.
McKenzie is likely to be on the bench with two from Deon Burton, David Mooney and Akpo Sodje set to start in attack.
Sodje is fully fit after a hamstring injury and has this week extended his loan spell from Sheffield Wednesday by a second month.