Chelsea striker Daniel Sturridge has until Friday evening to prove he has fully recovered from viral meningitis and is fit to take part with Team GB at the Olympics.
The 22-year-old only met up with Stuart Pearce's squad on Monday having earlier in July spent time in hospital recovering from his illness and missed a warm-weather training camp in Spain.
Ahead of Friday's friendly against Brazil at Middlesbrough's Riverside stadium, Sturridge's fitness will be closely monitored before Team GB consider applying to FIFA for a replacement.
"Daniel met with us today," Pearce told Sky Sports News on Monday. "Obviously he was taken in to hospital some 10 days ago.
"He did not come to Spain with us. He stayed at Chelsea. They have looked after him and we had our medical people going in and checking up on a regular basis.
"He has done some light work at this moment in time."
Pearce added: "We would have to know, probably, by Friday evening whether we feel as though he is going to be physically up to taking on a tournament of this magnitude.
"And then at that stage, if we do not, we have got to apply to FIFA in regard to getting a stand-by player to take his place.
"We have got our fingers crossed. Knowing the attitude of the lad, I'm hopeful (he will be fit)."