West Ham midfielder Robert Snodgrass has been added to the Scotland squad for the games with Belgium and Albania.
Snodgrass, 30, replaces West Brom forward Matt Phillips, who is injured.
The former Hull playmaker has not played for Scotland under Alex McLeish, but has been involved all four of West Ham's Premier League games this season.
Belgium provide friendly opposition on 7 September, with the opening match of the Nations League against the Albanians at Hampden three days later.
Rangers midfielder Ryan Jack was added to the squad on Friday after Tom Cairney's withdrawal, while Celtic defender Jack Hendry has also pulled out.