Jim Goodwin’s side only have 12 players available, four of whom are goalkeepers, for the Ladbrokes Premiership match after a number of positive Covid-19 tests among the Buddies playing squad.
League bosses postponed the fixture but will also launch a probe into the events.
Saints chief executive Tony Fitzpatrick described the situation as “disappointing… despite the numerous precautions and safeguards that are in place”.
He added: “This is hugely frustrating for our fans, the players and staff, and for everyone connected with the club.
"We will be working with the SPFL and relevant health authorities on this matter and will provide an appropriate update when more information is available.
"This once again underlines the absolute necessity of maintaining vigilance to ensure that players, officials and their families minimise the risk of infection to keep everyone safe."