Angus Gunn started in goal against Japan, but might Clarke be tempted to hand an opportunity to one of the other goalkeepers in his squad?
One would expect Craig Gordon to travel to the World Cup if he is fit, and challenge Gunn for the gloves, but Liam Kelly and Scott Bain are vying for the third spot.
Bain is the only one of the four playing regular football with his club Falkirk, but the most recent of his three Scotland caps came in March 2019.
There will almost certainly be changes in the back four though.
Clarke regularly changes his central partnership, and both Jack Hendry and Scott McKenna played the full 90 minutes against Japan.
Regulars John Souttar and Grant Hanley are the most likely candidates to start, but Wrexham’s Dominic Hyam is another option.
At right-back, Nathan Patterson looked rusty before being replaced by Anthony Ralston on Saturday.
Clarke knows exactly what those two offer, and with first-choice Aaron Hickey still out injured, could there be a start for versatile Bristol City defender Ross McCrorie?
Captain Andy Robertson and Kieran Tierney will likely share the left-back duties once more.