Nathan Patterson will not be available for Scotland's World Cup playoff clash with Ukraine on Wednesday.
The Everton full-back was called up to the camp for the crucial fixture having missed the end of the season due to surgery on an ankle problem.
Patterson arrived at Goodison Park in January in a signing that excited supporters, although he has yet to play a minute in the Premier League for the Toffees. In his only start - the FA Cup clash with Boreham Wood - he was withdrawn at half time.
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Nevertheless, such is his importance to Scotland - the 20-year-old has shone in his eight senior outings for the national side - he has been given every chance to be available for one of the upcoming games.
However, the showdown with Ukraine and a potential battle with Everton team-mate Vitalii Mykolenko will come too soon for Patterson.
"Everyone except Nathan," said Clarke when asked about player availability on the eve of the game. "Nathan has run out of time a little bit for the first game. So Nathan won't be involved in the first game but everyone else is good to go."
The winner of Scotland's clash with Ukraine with face Wales in Cardiff on Sunday, with the victor of that encounter securing a place at the 2022 World Cup in Qatar later this year.
Scotland also have upcoming fixtures against Armenia - home and away - and the Republic of Ireland in the Nations League, meaning Patterson should get a chance to get some crucial game time under his belt ahead of next season.
