Allen is keeping his cards close to his chest regarding their identity ahead of the encounter although he did reveal youngsters Devante McKain and Nathan Nyafli, a defender and forward respectively, have been called up to the squad.
Gills welcome back first-choice goalkeeper Stuart Nelson after he missed last weekend's 2-0 FA Cup defeat at Preston due to a one-match suspension.
Defender Connor Essam also sat out of the cup tie with a dead leg and it remains to be seen whether he will be fit to feature.
Tom Flanagan is still sidelined due to his fractured metatarsal.
Leaders Gillingham go into the clash boasting a two-point advantage over second-placed Port Vale.
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