It was confirmed on Tuesday that vice-captain Hariss Harun would definitely miss next Wednesday's game in Doha, although Singapore were initially hopeful defenders Safuwan Baharudin and Shakir Hamzah, and winger Yasir Hanapi would be made available.
The latter trio missed Saturday's 2-2 friendly draw against Azerbaijan, and it has now been confirmed by sources close to the Football Association of Singapore that the country's Ministry of Defence (MINDEF) has not granted Safuwan, Shakir and Yasir permission to join up with Radojko Avramovic's squad.
While the Lions stand no chance of progressing to the next round of World Cup qualifiers, this will still come as a blow for Avramovic's preparations, as all four are highly regarded within the Singapore camp, and are said to be integral to the team's future.
Hariss has been ever-present in the Lions midfield since making his international debut as a 16-year-old, while 20-year-old Safuwan has impressed with his maturity at the back since earning his first cap last year.
All four ply their trade for the LIONSXII, who are currently fourth in the Malaysia Super League after an impressive start to their 2012 campaign.