The 35-year-old Malaysian, Olympic silver medallist at the last three Games and Commonwealth Games champion on the Gold Coast in April this year, pulled out of the World Championships last week and will also miss the Asian Games next month as he has treatment for what is reported to be a serious respiratory illness.

In a video recording on the Yonex website in conjunction with its new racquet launch, Chong Wei said he hopes to meet up soon with other shuttlers, including Dan, who beat him in the Beijing 2008 and London 2012 finals.

On Saturday (July 28), NSTP Sport reported that Chong Wei was facing a career-threatening health problem and was in Taiwan for treatment.

"Thank you, Lin Dan for attending this activity [Yonex racquet launch in Nanjing] for me and I hope you do well. I will return to the court to see you as soon as possible... I love you all," Chong Wei said in the video.

Lin Dan responded: "I greatly appreciate my relationship with Chong Wei.

"From the first day to now, from single to being married and having our own families, we have a strong bond.

“I hope Chong Wei will get well soon and return to the court.”

Axelsen added: "I hope Chong Wei gets well soon and hopefully his medical treatment goes accordingly."

Both Lin Dan and Axelsen came through their men’s singles first round matches at the Nanjing Youth Olympic Sports Park today with respective victories over Mark Caljouw of The Netherlands by 21-14, 21-14, and Duarte Anjo of Portugal by 21-8, 21-7.

Another home hope, third seed Shi Yuqi, also got off to an assured start with  a 21-13, 21-11 win over 93rd-ranked Adam Mendrek of the Czech Republic.

But despite the victory, the 2018 All England Open champion was not satisfied with his performance.

"I have not got fully accustomed to the arena and [I haven't] given my best," Shi said.

"The first match was not satisfactory - I must play better in future matches."

The 22-year-old, winner the 2014 Summer Youth Olympic Games gold medal in the same arena, was reticent on the question of a possible meeting with Lin Dan: "I won't think too much about that.

"Lin Dan is the standard bearer for Chinese badminton.

"I just need to keep calm and demonstrate the energy and passion of the young generation."

Gregoria Mariska Tunjung, Indonesia’s 18-year-old world junior champion, underlined her reputation as one of the fast-rising prospects of women’s singles as she won an awkward match against Scotland’s European and Commonwealth Games silver medallist Kirsty Gilmour 21-18, 18-21, 21-14.

Tunjung is next due to face her predecessor as world junior champion, Chen Yufei, bronze medallist from the last edition of the World Championships.

England’s Chloe Birch dug herself out of a hole against Spain’s Beatriz Corrales, scrambling from 12-17 and 15-19 down to earn victory 21-17 21-19 and a meeting with 12th seed Beiwen Zhang, making her first World Championships appearance for the United States.