McStay, who missed last week's win at Partick Thistle because of suspension, is available to Tommy Burns, who is up against the club he quit to return to Celtic as manager.
Pat McGinlay would appear to be favourite to drop out to accommodate McStay alongside Phil O'Donnell, who will be making his home debut.
Kilmarnock have Tom Black suspended after being sent off against Falkirk last week. John Henry is winning his fitness battle and Shaun McSkimming and Ray Montgomerie are also in contention.
Dundee United, who had to come from behind against Tatran Presov to win 3-2 in the Uefa Cup on Thursday, visit bottom-of-the-table Hearts. United will be without the suspended Billy McKinlay but David Hannah hopes to recover from a strain that hampered him against the Slovakians.Reuse content