Marcus Fraser, who signed a new two-year deal on Friday, is back after he was injured in the warm-up before the last game against Hamilton.
St Johnstone have been hit with a major blow after four members of Callum Davidson's squad were ruled out following a Covid-19 outbreak.
The Perth club have reported two positive cases – with another two players ordered to self-isolate ahead of the Hampden clash due to track-and-trace rules.
Davidson has, however, received good news with quarter-final hero Zander Clark fit again after the toe injury which ruled him out last week against Hibernian, while Murray Davidson is ready to return after two months out with a calf injury. Scott Tanser (ankle) is out.