The Thais' 2-1 win over Philippines -- which also sealed the record five-time champions' progress -- at the National Stadium earlier in the evening meant there was no way Singapore could be overtaken inside the top two even if they finished level on points with either of Group A's other hopefuls due to a superior head-to-head record.
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It ensured that there would be no significant nerves for the Singaporeans ahead of their meeting with Timor-Leste, a game they would still have been expected to win comfortably yet -- with the pressure lifted -- the Lions contrived to produce an unconvincing display despite picking up a 2-0 victory through goals from Adam Swandi and Shakir Hamzah.
And it was not as though they had been affected by any real rotation, with Singapore coach Tatsuma Yoshida fielding largely his strongest XI boasting captain Hariss Harun, first-choice defenders Safuwan Baharudin and Irfan Fandi, and star striker Ikhsan Fandi among others.
Midway through the second half, with Singapore constantly moving the ball sideways and not displaying significant attacking intent, portions of the 8,000-odd crowd present started voicing their displeasure.
However, Yoshida was in defiant mood after the match and bristled at suggestions it was a below-par performance.
"We're the Singapore national team, not Spain, South Korea or Japan. The boys tried to play their best and I respect that," said Yoshida.
"If they (the fans) are here supporting the Spanish team, then that's okay. Of course, I'm not fully satisfied with the performance but I'm proud of the players."
Granted, it has to be noted that the Lions campaign as a whole has thus far been a positive one, especially given the last time they qualified for the last four was almost a decade ago in 2012.
Prior to Tuesday, their earlier Group A triumphs over Myanmar and Philippines were both creditable performances.
Yet, now that they are into the semis and expectations will increase, their display against Timor-Leste will raise doubts over their credentials to go all the way, if that is the target they have in sight.
Whether Yoshida likes it or not, the fact of the matter is that Singapore were expected to produce a dominant display on the night and failed to do so.
They will now have another chance to show they mean business although it will be a far different proposition to the Timorese.
A final Group A tie against Thailand on Saturday in an outright duel for top spot.