Young striker Moses had to be substituted towards the end of Tuesday night's goalless draw with Sheffield Wednesday after sustaining an ankle knock.
Defender McCarthy played despite a virus and boss Neil Warnock expects him to get worse before he gets better which could rule him out.
Fellow centre-half Davis was sidelined by the same virus in midweek but he could have recovered in time for Saturday and will be in line for his second Palace debut if McCarthy misses out.
Strikers Freddie Sears (ankle) and Stern John (elbow) are still out, although both should be close to returning after the international break.
