Sunderland full-back Phil Bardsley is poised to make his Scotland debut against Spain after manager Craig Levein confirmed Alan Hutton was a major doubt for the Euro 2012 qualifier.
Hutton has been struggling with a groin problem and was one of several players to sit out training on Sunday.
English-born Bardsley, 25, was called into the squad last week after pledging his allegiance to Scotland despite previously rejecting overtures from his Glaswegian father's nation.
Levein said: 'The biggest doubt is probably Alan Hutton. It looks as if he might struggle but I can't say for certain.'
With Levein already without the injured Kirk Broadfoot, he confirmed that a debut for Bardsley was a 'distinct possibility'.
Levein will assess the fitness of his other injury doubts in training before naming his team for the Hampden clash tonight.
West Brom midfielder Graham Dorrans has a hamstring problem while Steven Whittaker is still struggling with a calf knock.
Lee McCulloch, who was suspended for Friday's 1-0 defeat against the Czech Republic, will train today but is still a doubt with a hip problem, however skipper Darren Fletcher has fully recovered from a knock.
Eyes on the prize: Phil Bardsley (right) is primed to make his international bow
'I'll have a better idea after training who is going to be available,' the Scotland boss said.
Levein would not reveal whether Kenny Miller would return after the striker was dropped to accommodate Levein's much-criticised 4-6-0 formation in Prague.
But he did confirm that Gary Caldwell would not start after the Wigan player managed 75 minutes on Friday on his first appearance since undergoing two hip operations in the summer.
'He has recovered quite well,' Levein said.
'I'll wait until after training to see if he can be included on the bench.'
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Explore more:People: Darren Fletcher, Gary Caldwell, Alan Hutton, Craig Levein, Kirk Broadfoot Places: Prague, Spain, Scotland, Czech Republic, United Kingdom