Reading midfielder Emerse Fae is recovering at home after having been diagnosed with malaria.
The Ivory Coast international travelled with his team-mates to Middlesbrough for Saturday's Premier League clash, but appeared to be suffering from a virus by the time the squad arrived.
"He looked terrible when we got up to Middlesbrough," manager Steve Coppell told the Reading Evening Post.
"He was sweating really badly so we just thought it was flu."
The midfielder was then taken back Reading, where it was revealed he had contracted malaria while playing for his country in the Africa Cup of Nations.
"We flew him back on Saturday. He came into training on Sunday and felt better, but by that evening he felt worse and he went to hospital where blood test showed he had malaria.
"He was taking malaria tablets out in Ghana so we're not sure how he got it."
Malaria, which is passed on to humans by infected mosquitoes, can put those infected into a coma or even kill.
However, Fae has been treated by medical experts and Reading physio Jon Fearn is confident that the player will make a swift recovery.
"It appears that Emerse picked up malaria when he was in Ghana for the African Cup of Nations and it lay dormant for a couple of weeks before coming out over the weekend," he told the club's official website.
"He received prompt treatment and is now under medication. He is recovering well at home and shouldn't be out for too long."