The Welshman picked up a muscular problem during Wednesday's Champions League victory against Bayern Munich and had to be substitued.
And now it has been confirmed that the 27-year-old forward has an issue with his right soleous muscle (lower leg) that could be connected to the ankle injury that was operated on in November.
It means that Bale, who missed training on Friday, is a doubt for the return leg against Bayern at the Santiago Bernabeu on Tuesday.
Pepe will also be missing from both matches with two broken ribs, while Raphael Varane has a thigh injury.
Read the full article on eurosport.co.uk: Bale to miss Gijon match, is doubt for return leg against Bayern in Champions League