They had high hopes of a top-six finish in the final leg of the HSBC Asian Rugby Sevens Series held here.
The Singapore Sevens' team have not finished in the top six in the four-city series this year.
Reaching that first tier would see them move into contention to make the Asian Games in Incheon next year - as required by the Singapore National Olympic Council.
A win against China at the Yio Chu Kang Stadium yesterday would have steered the Republic towards that target, but Daniel Marc Chow and Co put in a woeful shift after a bright start and lost 24-14.
Singapore led 14-0 after the opening five minutes, but sloppy passing and lethargic play allowed the visitors to cut the deficit to 14-12 by half-time, before the Chinese motored away in the second seven-minute period.
Singapore Rugby Union technical director Inoke Afeaki was livid after the match, and said: "That was probably our worst performance in a long time. We had the players and the game plan to come out with a result but we made some really uncharacteristic errors.
"We talked about (doing) altitude training but we didn't mention that attitude is what counts. You have to have a tough attitude to turn up and put in some tough work."
Captain Chow said: "We did really well in the first five minutes but we just lost concentration in the last two minutes of the first half."
"The boys were getting really excited and eager to get the ball back and we just lost our composure after that," added the 29-year-old, who received seven stitches to his lip after being caught in the face by a stray elbow.
In their following Pool A game, the hosts were then thumped 36-0 by powerhouses Hong Kong, although Afeaki was much happier with the performance against one of the favourites.
The Tongan said: "The scoreline flattered our opponents and the boys played much better than they did this afternoon.
"They put in more effort and the tackling was better. We should have scored a try in the dying minutes but it wasn't given.
"Hong Kong were on fire and we held them close in the first few minutes, but they came here with their guns blazing."
Singapore will face Indonesia this afternoon in the Bowl semi-final and will be missing vice-captain Bryan Ng.
He suffered a sprained ligament in his foot after the China game and will be out for two or three weeks.
Said Chow: "It is quite disappointing that we didn't achieve our target; it is a real waste because we were really progressing well in the last three series.
"But now, we really want to win the Bowl final, which will put us in ninth place for the Singapore leg."
To the approximately 1,000 fans who turned up yesterday, Chow said: "We're sorry we let Singapore down."
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