The 25-year-old is set to move from Club Brugge to the Amex but international clearance has not come through in time for him to face the Citizens this weekend.
However, Chris Hughton can call on new midfielder Davy Propper, who was signed from PSV Eindhoven, as the Seagulls make their Premier League bow against the favourites to lift the trophy next May.
Midfielder Beram Kayal will miss the next two months with a broken leg and Brighton will assess winger Anthony Knockaert, who is close to a return after injuring ankle ligaments in July.
Other new recruits Mat Ryan, Pascal Gross and Markus Suttner are in with a chance of playing some part.
Provisional squad: Ryan, Maenpaa, Bruno, Dunk, Rosenior, Suttner, Bong, Stephens, Gross, Propper, Knockaert, Sidwell, Skalak, March, Gross, Murphy, Brown, Hemed, Murray.