Grealish missed Saturday's 1-1 FA Cup third round draw at Wycombe Wanderers with tonsillitis, while Richards was forced off in the closing stages of the match after injuring his foot.
The 20-year-old playmaker missed Saturday’s 1-1 FA Cup third round draw at Wycombe Wanderers after contracting the illness in midweek and Garde does not expect him to be back in time for the match at Villa Park.
Speaking after Saturday’s game, the former Lyon boss said: “Jack was ill for the last three days with tonsillitis. He hasn't trained for the last three or four days.
“He hasn't trained with a fever. He has antibiotics.”
Micah Richards’ status for Tuesday night is also up in the air after he picked up a knock against Wycombe.
The team captain, who started the match at right-back in place of the injured Alan Hutton, opened the scoring in the 22nd-minute with a low right-footed shot but was later forced off with a foot problem in the 83rd-minute.
Garde stressed at the final whistle that he did not think the issue was too serious but added that he would need to speak to the club’s medical staff before getting a clearer picture on whether his skipper would be able to feature against Palace.
“I don't know exactly,” Garde said on the extent of Richards’ injury. “He had to come off - and I did it.
“I haven't spoken with the doctor yet. I don't think it's very important - but it was important enough for him to ask to come off.”
Richards was replaced by debutant Jordan Lyden at Adams Park, but the 19-year-old Australian played the final seven minutes of the match in midfield while Leandro Bacuna was shifted from the wing to right-back.
The utility man will likely start at the position against Palace if Richards’ injury is worse than first feared, with first-choice Hutton expected to be sidelined for at least a couple more games after tweaking his hamstring in last weekend’s 3-1 loss at Sunderland.