Middlesbrough boss Gareth Southgate says the club are keeping a close eye on Robert Huth's fitness as they still hope to sign the defender.
Huth has struggled for first-team football at Chelsea
Centre-back Huth was set to join from Chelsea for £5m but failed a medical because of an ankle injury.
"I wouldn't want to put it in percentage terms because it is a bit of an unknown," said Southgate.
"We were disappointed not to have been able to do it but we are still monitoring the situation."
Huth missed most of his country's World Cup campaign because of the injury and it is thought that it could be more serious than was first thought.
He arrived in Middlesbrough for a medical on 9 July but the transfer failed to materialise.
Berlin-born Huth managed only 32 senior starts during his five years at Chelsea and just one of Germany's games at this summer's 2006 World Cup.
Southgate added: "Robert unfortunately had an injury in the World Cup that he reported with.
"We needed to be a bit clearer about it before we were able to sign him. But we are in discussions with Chelsea to see how it's progressing."