By Ian Ransom

RIO DE JANEIRO (Reuters) - China's failure to defend three of its badminton titles at the Rio Games was a shock for a nation used to dominating the Olympic courts but head coach Li Yongbo called for calm amid a storm of criticism.

Four years after winning all five titles at London, China grabbed two gold medals and a bronze to top the medals table, but it was their lowest haul at an Olympics for 20 years.

With teams restricted to two entrants in the singles, down from three at London and previous Games, the badminton superpower had fewer chances to win medals.

However, the lack of a Chinese woman on the podium for both the singles and doubles was a major setback for a team that had built long dynasties in both events.

Li has been the face of Chinese badminton for over a decade and survived a number of controversies by delivering unprecedented results at global and Olympic tournaments.

But the 53-year-old has been lambasted online over the team's performance in Rio, with Chinese social media users demanding his resignation.

China will lose at least two of its Olympic gold medalists to retirement, with doubles veteran Fu Haifeng and twice singles champion Lin Dan playing their last Games.

Zhao Yunlei, who won mixed doubles gold at London and took bronze in Rio, is also tipped to quit before Tokyo in 2020.

Li said China had little to fear about the passing of the golden generation but conceded there would be more challenges as rival nations closed the gap.

"Sometimes you’re strong, sometimes you fall back," he told Reuters.

"Indonesia was once strong and Denmark, too. China's risen up but the champions eventually retire and the next generation comes up slowly.

"So there will be some difficulties. This is normal.

"But China will still have top players competing in future because we have a lot of juniors competing at high levels.

"After these Olympics, our next generation will be strong.

"For a country to maintain its excellence it definitely needs to emphasize systemic talent development and very good training systems. China has, so I am not worried about (the future)."

Indonesia, Spain and Japan won the other titles in a high-quality tournament that spread the medals far and wide.

"Badminton is developing on all sides," said Li.

"But there is no point judging everyone else’s progress, it’s a matter of concentrating on your own.

"It is fair to say we have more difficulties than before but that does not mean we are going to fall behind. It is just others are progressing, so we still need to work hard."

(Editing by Meredith Mazzilli)