Scotland captain Andy Robertson has been ruled out of their opening Euro 2020 qualifier in Kazakhstan, the Scottish FA said on Tuesday.
The Liverpool left-back has had an operation on an abscess in his mouth, the BBC reported, and the Scotland medical team are hopeful he will return to the squad for their next match in San Marino on Sunday.
Celtic defender Kieran Tierney is likely to deputise at left-back in Robertson's absence as Scotland begin their bid to qualify for the European Championship for the first time since 1996.
Scotland boss Alex McLeish could introduce some fresh faces in his side for the match in Astana on Thursday with up to five players in line to make their debuts.
Hibernian striker Marc McNulty, Sheffield Wednesday defender Liam Palmer, Sheffield United midfielder John Fleck, Livingston goalkeeper Liam Kelly and Kilmarnock defender Stuart Findlay could all win their first caps.
Scotland were drawn in Group I for the qualifying campaign alongside FIFA's top-ranked side Belgium and World Cup quarter-finalists Russia.
Only the top two in the group are guaranteed a spot at the tournament, although Scotland are ensured at least a playoff place having won their UEFA Nations League group.