Thursday's announcement has led the local media to suggest Radojko Avramovic's future as Lions coach is now clouded in doubt.
Singapore matched their best-ever showing by reaching the third round of the AFC World Cup qualifiers, but ended their campaign bottom of Group A.
In addition, the Lions failed to win a single game against China, Iraq and Jordan and conceded 20 goals in six matches, scoring just twice in the process.
And while FAS president Zainudin Nordin accepted the Lions had met the goal set before the start of their campaign, he revealed country's governing body were still going to review the team's 'disappointing' performances.
"While the national team met our target of reaching the third round of the 2014 FIFA World Cup Asian Zone Qualifiers for the second consecutive time, we agree that the players and coaches involved in the six World Cup Asian Zone Qualifying matches could have performed better," Zainduin said in an FAS press release.
"Like our fans, we are disappointed with the results and we agree there is much room for improvement in the team's performances.
"However, we acknowledge that these qualifiers have provided an invaluable opportunity for many U-23 players to gain international exposure and the top level, and this is in line with our objective of rejuvenating the national team."
The FAS will now await a report from Avramovic before deciding on what actions need to be taken to ensure Singapore's progress in the future.
"Following the conclusion of the third round of the 2014 FIFA World Cup Asian Zone Qualifiers, FAS will await the coach's report and analysis of the entire campaign," Zainudin added.
"In line with our practice, the FAS ExCo [executive committee] and Council will subsequently review the post-tournament report and assess the team and coach's performances during the entire campaign before considering what action needs to be taken."
Avramovic's preparations for Singapore's qualifying campaign were not helped by several key players' National Service (NS) commitments.
Most recently, vice-captain Hariss Harun, defenders Safuwan Baharudin and Shakir Hamzah, and winger Yasir Hanapi were all denied leave to participate in the Lions' final qualifier against Iraq on Wednesday, which ended in a 7-1 defeat.