The Merseyside club will travel to face the Royals without the Belgian international forward and the Irish midfielder, having lost the pair to injury ahead of Saturday's game
Belgium international Mirallas suffered a hamstring strain in last week’s 2-1 win over Sunderland, while Irish international Gibson has been out since September with a thigh problem.
In his pre-match press conference, Moyes told reporters: "Kevin is out injured, but we don't think it's too bad at the moment. Darron is still injured."
Striker Victor Anichebe and right-back Tony Hibbert will undergo fitness tests on Friday but are doubtful, having missed last week’s victory over the Black Cats, with Seamus Coleman and Steven Naismith possible replacements.
The Toffees are currently fourth in the Premier League, while the Royals are yet to win a top-flight match so far this season.