A third-placed finish on the medals table below the United States and Britain, made for a sobering Games after China triumphantly topped the standings at Beijing 2008 and finished second in 2012.
"You kidding me? The country which has never finished above China is about to," spluttered the official Xinhua news agency, in a tweet that was later removed.
As well as their lowest gold medals tally (26) since Atlanta in 1996, when Jiang Zemin was president, China were also left smarting on a couple of occasions.
Later, China complained, but again to no avail, after the United States were allowed to re-run their women's 4x100m heat, knocking the Chinese team out of the event and eventually winning gold.
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A Xinhua commentary said the re-run was against the "Olympic spirit of fairness" and was "widely regarded as ridiculous and unfair".
Liu Peng, head of China's Olympic committee, said China would learn lessons from Rio, when rising standards in other teams had taken them by surprise.
Of the 410 athletes, the most China has ever taken to an Olympics away from home, 73 percent were at their first Games, Liu said.
It points to a rebuilding phase ahead of Tokyo, capital of China's war-time rival and former colonial power which still evokes bitter resentment among many Chinese.
- 'More than a champion!' -
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"We have trained these (young) athletes but the training isn't enough," he said.
"Because when these athletes are facing fierce competition and challenges, they have too much to think about and too many mental burdens and they didn't play at their highest level."
medals in diving, but even there their rivals seemed to be closing the gap.
In gymnastics, where China won four gold medals in London, they won none at all in Rio, prompting comments from the sport's boss that China need to move with the times.
"They've remained trapped in a robotic style of training," FIG president Bruno Grandi told AFP.
China's silver lining came in the behaviour of their athletes, who unusually showed their human side and won new fans, at home and abroad, in the process.
Swimmer Fu Yuanhui shone through with her warm personality and honesty, even to the extent of talking about her periods, while Qin Kai proposed to fellow diver He Zi as she stepped off the Olympic podium.
"Today, the Chinese need the fighting spirit of the women's volleyball team more than ever," Xinhua said in an editorial.
"As individuals, living in a time of drastic change with both opportunities and challenges, one needs the spirit to go sure-footed and step by step to reach afar."
"To be a champion, more than a champion! May the fighting spirit of the Chinese women's volleyball team be always with us," the editorial added.