Jack Ross makes one change to the side that defeated Queen of the South last Saturday.
Cammy Smith is cup-tied and John Sutton comes in in his place. The striker has scored four goals for Saints in the run to the final and partners Rory Loy up front.
Stevie Mallan also starts for the Buddied on his 21st birthday.
St Mirren: O'Brien, Irvine, Baird, MacKenzie, Eckersley, McGinn, Mallan, Magennis, Morgan, Sutton, Loy
Subs: Langfield, Webster, Fjelde, Stelios, O'Keefe, Whyte, Watters
