Heitinga has been out of action for some time now due to a knee problem, while the former Sheffield United man hobbled off during the recent victory over Manchester City with a thigh injury.
"'Jags' has a bit of a thigh strain," Moyes said on the club's official website.
"He hasn't trained all week and it was a doubt whether he could play.
"He got through most of the game but with Johnny Heitinga injured I have run out of centre-halves at this point so I will need to hope I can get them fit for Boxing Day."
Everton take on Birmingham, West Ham United, Stoke City and Tottenham Hotspur in a 10 day period starting from Boxing Day.