They were supposed to have lined up for the Singapore Under-23s in a friendly match against Cambodia last Friday.
Instead, Al-Qaasimy Rahman (first inset), Fazli Ayob (second inset)and Syafiq Zainal (third inset) found themselves lying on hospital beds over the weekend.
Tests showed the three footballers, who are in Aide Iskandar's provisional South-east Asia Games (SEA) squad, contracted dengue fever.
Defender Al- Qaasimy, 21, looked worse for wear when he sat out training last Thursday.
He had trouble sleeping later that evening and went to the Changi General Hospital - where he was warded - at about 4am on Friday morning.
Winger Fazli, 23, and 22-year-old striker Syafiq, meanwhile, took part in training but were left out of the team for the match.
They were warded at the Raffles Hospital, just hours after the match, which Singapore lost 1-0.
"We first felt it (the effects of the fever) after training on Thursday," said Syafiq. "Our legs just felt lembik (soft in Malay), but we didn't think too much of it.
"The next morning, the weakness and aching were not so bad. But just before the game, the fever went up again."
Syafiq and Fazli are recovering well, and could be discharged today. Al-Qaasimy, however, is still being monitored and doctors could not confirm when he would be discharged.