St Mirren striker Kristian Dennis faces a lay-off after picking up an injury during the midweek defeat by Hibernian.
Dennis came off in the 38th minute to allow Dean Lyness to take over in goal following Jak Alnwick's red card, but the forward was also struggling and will miss Saturday's visit of Kilmarnock.
Manager Jim Goodwin said: "There will be a couple of changes in personnel, obviously with Jak's suspension and Kristian Dennis unfortunately looks to have hurt his Achilles. He is away for a scan so we will need to wait and see what the outcome of that is."
The news is a blow given Dennis scored in the previous two matches in victories over Dundee United and Celtic.
"Denno has worked really hard on his fitness," Goodwin said. "He was behind when he came to the club because he came in so late and hadn't really had the opportunity to do a proper pre-season.
"Junior Mendes, the sports scientist, has been working tirelessly with Kristian to get him up to speed. He has lost a lot of body fat, he has lost a couple of kilos as well, and I think that has shown in the last three or four weeks in his levels of performance.
"He looked a lot sharper, looked a lot livelier in the games he has played, and chipped in with a couple of really important goals against United and Celtic.
"He'll be a loss, no doubt about it, because we were looking forward to seeing how he progressed in the second half of the season.
"Hopefully the scan doesn't show too much damage and fingers crossed it's only a couple of weeks."
Saints had Lee Erwin back on the bench after injury during the 2-1 defeat and another attacker Collin Quaner is not far away from a comeback from a knee problem.
"Collin Quaner is making great progress," Goodwin said. "We are hoping, not to push him too quickly, but we are hoping that Collin will possibly be available for the following weekend, which is a great boost to the squad."
