Scotland have doubts over several defenders ahead of their opening World Cup qualifiers against Serbia and Macedonia.
Southampton left-back Danny Fox, Norwich's Russell Martin and Celtic's Charlie Mulgrew all reported to Scotland's Mar Hall base with injuries, while Wolves centre-back Christophe Berra was excused from turning up on Monday as he awaits the birth of his first child.
"The good thing is we have got a few days, sometimes injuries settle down after 48 hours. We'll keep everyone informed," assistant manager Peter Houston said as he confirmed Fox has a groin strain, Martin an ankle knock and Mulgrew is struggling with Achilles pain.
Besiktas goalkeeper Allan McGregor is confident of being fit after recovering from the groin strain that forced him off in the friendly win over Australia last month.
"He played on Saturday and kept a clean sheet," Houston said.
"We are absolutely delighted he's fully fit because his experience in playing big international matches is vital.
"We were convinced after the Australia game that he was struggling. He had a couple of injections and recovered brilliantly. Fair play to the (his club) for getting it sorted."