Scottish Cup final: Touch and go for United pair
Winger Mackay-Steven is still trying to shake off a chest infection while defender Souttar is only just recovering from a bout of flu ahead of the clash with St Johnstone.
Curtis Good will definitely miss out on the big day after he was allowed to join up with the Australian World Cup squad early, as will the injured Calum Butcher (toe).
Provisional squad: Cierzniak, Watson, Wilson, Robertson, Souttar, Gunning, Dillon, Paton, Mackay-Steven, Rankin, Armstrong, Ciftci, El Alagui, Gomis, Dow, Graham, Gauld, Connolly, McCallum.