Several members of the national football team have expressed disbelief at allegations that some Lions had committed breaches of discipline and that these incidents involved team manager Farehan Hussein.
The issue came to light yesterday when it was reported that the 34-year-old is being investigated by the Football Association of Singapore (FAS) over the allegations.
The instances of misconduct are alleged to have occurred while the Lions were on international duty.
The inquiry is believed to have been prompted by a formal complaint that reached local sports governing body Sport Singapore (SportSG).
It has asked the FAS to look into the matter. Some FAS staff and players have already been called up to give their statements to the investigation panel.
The issue could not have come at a worse time for the Lions, who are preparing for a series of key matches.
Singapore will play a closed-door friendly against Myanmar next Tuesday, followed by the AFC Asian Cup qualifier against Chinese Taipei next Saturday.
Both matches will be played at the Jalan Besar Stadium.
On June 13, the Republic will host two-time World Cup winners Argentina in an 'A' international friendly at the National Stadium.
Referring to the allegations, national captain Shahril Ishak said: "I'm 100 per cent certain that nothing happened. It's ridiculous to hear of such things.
"It's just accusation, without any proof, from someone who wants to sabotage the team. We've got to prepare for the matches that are coming up.
"Farehan is a responsible person and there's no problem with him and the national team.
"Our welfare has always been taken care of. In fact, he would always remind us about what we should or shouldn't do, as adults."
Veteran goalkeeper Hassan Sunny said he also believes that there is little truth to the allegations.
He said: "I think it's all false allegations. He's a hard-working, reasonable and nice person whom we trust and respect.
"I don't think that this is a big issue and it will not affect the team's preparations."
Allegations of indiscipline within the Lions' ranks are not new. In the past, players were punished for breaking curfew, boarding the team bus late, staying up late, drinking alcohol and gambling in hotel rooms.
Hassan insisted that the players are aware of the obligations that come with pulling on the Singapore jersey. He said: "I would always tell myself when I'm overseas that I'm not there on a holiday. So we've got to be careful of how we behave because we represent the country."
Farehan could not be reached for comment.