A second, unnamed, St Mirren player has tested positive for Covid-19 following confirmation that goalkeeper Jak Alnwick is already in self-isolation.
Alnwick's housemate, Lee Hodson, the former St Mirren full-back now with Hamilton Academical, is also having to quarantine for 14 days.
The goalkeeper started his 10 days of isolation after Monday testing.
After a fresh set of tests on Thursday, St Mirren said they "can confirm that a second player has tested positive".
While St Mirren said they would make no further comment about the player's identity at this stage, it means he will join Alnwick in missing the Paisley side's games against Hibernian and Celtic.
Manager Jim Goodwin said earlier he would normally be reluctant to reveal personal details but had said of Alnwick: "Somebody has leaked it out there on social media and there's no point us denying it.
"It would be perfectly clear to everyone when the team is selected on Saturday anyway. We are disappointed for Jak, but he's doing well and recovering."
Alnwick's positive case was picked up during the Scottish Premiership club's twice-weekly testing and, following the second positive test, they again stressed that they had "followed all protocol to the letter".
Unlike Hodson, who has to isolate for 14 days having come into contact with a positive case, the goalkeeper's 10-day quarantine leaves Goodwin hoping he can return for his side's game against Dundee United on 19 September.
"The two lads have been close pals for a number of years and Lee Hodson came up the road to Hamilton just recently, so this was a temporary arrangement," Goodwin explained.
"We were satisfied because we know that Hamilton are in the same situation as ourselves and are adhering to the guidelines as we are. We worked with Lee last season - two very professional lads who would most definitely be sticking to what's been asked of them.
"It is just an unfortunate situation where Jak has caught it and Lee is having to isolate as well because they are living together."
St Mirren had seven members of staff test positive for Covid-19 in July, but six were found to be false-positives after further screening and Goodwin insisted that Alnwick had followed all the protocols.
"This is just something that is going to continue to happen through the course of the season as long as this virus is here," he said. "What I can say is that there's no way Jak has picked it up while he's been here at Ralston [training ground] or down at the stadium.
"We can't do any more as a club at our end, but unfortunately the players and the staff members, everybody has to go home and some of our partners and wives are going out to work every day and I've got three kids going to school every day mixing with hundreds of other children."
Alnwick has started all five of St Mirren's games this season, which means fellow Englishman Dean Lyness is poised for his first first-team start since turning out for Raith Rovers in May 2019.
"Jak has been excellent and has been one of the more consistent members of the squad," Goodwin said. "He's my first choice goalkeeper and has made some key saves.
"Of course he is a loss, but I'm very fortunate in having a very good back-up in Dean Lyness, who will be excited to get this opportunity."