Scotland will be without Stephen Crainey for the forthcoming Euro 2012 qualifying games away to Liechtenstein and Spain, and Kenny Miller could also be missing.
The Scottish Football Association confirmed that Blackpool defender Crainey will be replaced by Lee Wallace of Rangers due to an ankle injury, while the Scotland medical team will assess Miller's groin complaint over the next 24 hours.
Craig Levein's squad will meet officially at their camp on the outskirts of Glasgow on Monday and the manager will be hoping for some good news on the Cardiff City player who, if fit, will almost certainly play in both games.
Miller was substituted early in Cardiff's 2-1 defeat at Hull City on Saturday and Bluebirds boss Malky Mackay said he would be "very surprised" if his player recovered in time for the two matches.
The former Rangers and Celtic striker scored one and set up the other goal in the 2-2 home draw with Czech Republic in September but missed the following 1-0 win over Lithuania at Hampden through suspension.
Levein has already lost midfielder Scott Brown, who is set to see a specialist about his on-going ankle problem.
The Scotland boss originally made three changes to his 25-man squad for the games in Vaduz on 8th October and against the world and European champions in Alicante the following Tuesday.
Brown's absence paved the way for a first call-up for Dundee United midfielder Danny Swanson, Cardiff goalkeeper David Marshall came in for Preston's Iain Turner, while Middlesbrough defender Stephen McManus returns to the squad with Liverpool centre-back Danny Wilson dropping out.