Scannell made his first appearance of the season in Saturday’s 1-1 home draw against Blackburn but suffered a slight recurrence of the problem and is not expected to be risked.
Strikers James Vaughan and Joe Lolley are expected to return to contention for their first appearances this season.
Vaughan has yet to feature due to the effects of concussion and Lolley has been struggling with a shin injury.
Brighton could add Jamie Murphy to their squad after signing the winger from Sheffield United on Friday but striker Bobby Zamora’s second debut for the club remains on hold due to a tight groin following training over the weekend.
Boss Chris Hughton must decide whether to recall Lewis Dunk, who has been linked with a move to Newcastle and Fulham. The defender was left on the bench for Saturday’s 2-1 win at Craven Cottage.
Summer signing Jack Harper is still recovering from an ankle problem but Hughton, whose side won both their opening games, has no new injury worries.
Midfielder Andrew Crofts, sidelined since October with a knee injury, is due to play for the Under-21s on Monday with a view to being involved against Blackburn on Saturday.