Sidley hit by injury and suspension
Captain Chris Copley is a doubt after he needed six stitches in a head wound suffered in last weekend's league game against East Preston.
Mark Freeman is in the midst of a 35-day suspension and joint player-manager Peter Heritage is suffering from an ear infection.
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Hide AdThe Blues travel to Eastbourne Town on Wednesday in the Sussex Senior Cup second round without Adam Day and Kevin Rose who two days earlier start 35-day suspensions.
United have tried to bolster their squad with a seven day approach for Westfield striker Duncan Jones.