Atletico Madrid are increasingly concerned over Diego Costa's fitness as they attempt to close his signing with Chelsea.
Marca says he now hasn't played a competitive game for 100 days and is training on his own.
Atletico are growing increasingly wary of his conditioning.
It's suggested he'll be seriously put through his paces if a deal gets over the line.
A deal totalling €65m (£57m) is now on the table.