There is no way of knowing how long Tottenham goalkeeper Hugo Lloris will be sidelined following his head injury at Everton, according to a spokesman from ImPACT Applications.
Despite playing on at Goodison Park after being knocked unconscious in a collision with Romelu Lukaku, Lloris has sat out Spurs' last two fixtures with manager Andre Villas-Boas confirming he was not risked in Sunday's defeat to Newcastle after failing to come through Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) - a computerised concussion evaluation system.
France captain Lloris has been called up for his country's World Cup qualifying play-off against Ukraine, but it is still unclear as to whether the 26-year-old will be involved.
"There is no hard and fast rule in how long a recovery can take," said Dr. James Gyurke from ImPACT Applications:
"Everybody reacts to it differently. In a concussed state the recovery period should be viewed as occurring over several days to weeks, not a single day. There is no prescribed timeline for someone."
With 80 per cent of people usually recovering from concussion within six to 10 days, Lloris is now in the window to show signs he is close to a return.
Gyurke explained the ImPACT System would have only formed part of a medical examination that led to Lloris being declared unfit and also suggested staying on at Everton may not have been the right decision.
"Getting up and carrying on with the game is not a wise thing to do if there is a suspicion the athlete has suffered a head injury," he told Press Association Sport.
"There is some data that suggests it is likely you are more susceptible to further mild traumatic brain injuries, though this is not definitive.
"ImPACT is not a diagnosis and does not provide a diagnosis. It is a tool. It is like the results obtained from an MRI scan. The test doesn't tell you to keep an athlete in a match or take them out but it is a piece of data the medical professional should use to form his or her clinical decision.
"When you're talking about an individual's level of impairment post injury, an athlete may under-report the severity of the symptoms he or she is feeling or experiencing in an effort to return to play. However, they generally can't distort their test performance, it is very accurate."