Craig Levein has drafted Huddersfield Town's Paul Dixon and Gary MacKenzie of MK Dons into his Scotland squad ahead of their opening World Cup qualifiers.
Southampton left-back Danny Fox (groin) and Norwich City defender Russell Martin (ankle) have been ruled out of the first game against Serbia at Hampden on Saturday, while Scotland will also take on Macedonia next Tuesday.
Former Dundee and Dundee United left-back Dixon, 25, has been capped at Scotland Under-21 level while former Rangers and Dundee defender MacKenzie, 26, has yet to win his first international honour, although both players have been in senior squads in the past.
One left-back manager Levein may have turned to, Lee Wallace of Rangers, has a hamstring injury.
Celtic defender Charlie Mulgrew reported to Scotland's Mar Hall base with an Achilles injury while Wolves centre-back Christophe Berra was excused from turning up on Monday as he awaits the birth of his first child, due on Tuesday.
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," said assistant Scotland manager Peter Houston.
"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 (his club) for getting it sorted."
Scotland go into the game without the country's most expensive player, Steven Fletcher, who repaid some of his £12million fee when hitting a double for Sunderland on his Premier League debut for the club in a 2-2 draw at Swansea on Saturday.
But Houston brushed off the reminder of what Scotland are missing out on amid the striker's continuing failure to contact manager Levein after pulling out of a squad 18 months ago.
"You look at Jordan Rhodes, who has been in excellent form and got an £8million move," he said.
"Kenny Miller has settled in well and another lad who has been with us, (Craig) Mackail-Smith, who didn't make the squad, his two goals were absolutely sensational at the weekend.
"It's a department we are well off in. We are thinking positive and looking forward to it with the group of players we have got.
"Ross McCormack scored in the Championship, what a goal he scored. There are guys who are naturally good goalscorers."