The defender, 26, got off his sickbed to take part in Sunday´s 3-3 draw against Dundee United but is still struggling with a virus ahead of the quarter-final, second leg tie.
Manager Walter Smith is already without the suspended David Weir ahead of Thursday´s clash and admits his defensive resources would be stretched to the limit if Cuellar was ruled out as well.
Copyright (c) PA Sport 2008, All Rights Reserved.
Do YOU want to write for GiveMeSport? Get started today by signing-up and submitting an article HERE: https://www.givemesport.com/writeforgms