Steven Naismith reveals how long Nathan Patterson has to prove fitness for Scotland

The 20-year-old right-back has struggled for game time at Everton since moving from Rangers in January and had ankle surgery at the beginning of April.

Naismith is confident Patterson, who has not played since Scotland drew 2-2 with Austria at the end of March, will not let down his country if he is declared fit for the crunch game at Hampden Park on Wednesday night, the winners of which will take on Wales in the play-off final in Cardiff.

After a training session at Scotland's base in Oriam, Edinburgh, Naismith said: "Nathan was on the pitch. He is obviously the one who came in with being injured but he has the next two days on the pitch to show that he is ready and fit.

"I think he is probably one of the ones in the squad that I have compared, in terms of his natural fitness, to Alan Hutton, who went long periods and never played (for his club) but performed well for Scotland.

"Nathan has shown that when he wasn't playing for Rangers, he played for Scotland, he played very well.

"So from that side everyone is comfortable that he could be ready and be in contention. But there is still two days for the manager to pick the team."

It was confirmed earlier that Ryan Jack is out of the squad to face Ukraine, with Clarke drafting in the uncapped Luton Town midfielder Allan Campbell, 23, coming as a replacement.