The Norwich player who tested positive for coronavirus has now returned a negative sample, says the club's sporting director Stuart Webber.
The Premier League side confirmed the positive test on Saturday, a day after they played Tottenham in a friendly.
Webber said the unnamed player will now have a third test that will check if he has antibodies to the virus.
"Luckily the player in question is completely fine - 100%. There's nothing wrong with him," he added.
The player was asymptomatic but, as per Premier League protocols, will continue to self-isolate until he tests negative with the league.
Speaking to the Beautiful Game podcast, Webber said: "He's actually done an independent test with our doctor which has come back negative, which is confusing.
"Now he's got to have a third test to see if that comes back negative and to check if he's got antibodies, which could prove that he has had it in the past but doesn't have it now.
"The main thing is that he's healthy and the rest of the group are healthy, but it's a good wake-up call. We've done all of these measures and one of us could still get it, that's quite scary really."
Norwich, who are bottom of the table, host Southampton on Friday (18:00 BST kick-off) in their first Premier League game since English football was suspended on 13 March.
Spurs, who welcome Manchester United at 20:00 the same evening, said none of their players would need to isolate because they were not "close contacts" of the affected player, who was involved in the friendly at Tottenham Hotspur Stadium.
The government defines a close contact as someone who has been within two metres of an individual who has tested positive for more than 15 minutes.