SINGAPORE - The rigours of back-to-back competitions at the highest level took its toll on national shuttler Yeo Jia Min, who retired while trailing 21-7, 15-9 to Thai world No. 12 Busanan Ongbamrungphan in their Badminton World Federation World Tour Finals Group B match on Thursday (Dec 2).

It was clear the Singaporean world No. 17 was up against it from the opening frame at the Bali International Convention Centre when she required treatment on her right knee.

Despite trying to fight on and taking a 3-0 lead in the second game, the 22-year-old just could not keep up with her 25-year-old opponent, and she decided to stop the match after 31 minutes.

This loss follows a 21-11, 21-14 defeat by Japan's world No. 3 Akane Yamaguchi on Wednesday.

Yeo will also miss Friday's match against South Korea's world No. 6 An Se-young, which means she will not make the semi-finals, although she should keep the US$9,000 (S$12,280) for making the season-ender.

In an Instagram story, Yeo wrote: "Retired because I did not want to make it worse before World Championships. I'm sorry to the fans.

"I will take care and strengthen the body now and be back again!"

While it is not the World Tour Finals debut Yeo would have envisioned - she is the first Singaporean to qualify for the US$1.5 million event which features the top eight singles and doubles performers of the calendar year - she was not the only player to retire.

In the men's singles, Japan's world No. 2 Kento Momota and Denmark's world No. 10 Rasmus Gemke also withdrew on Wednesday, which mean Denmark's top-ranked Viktor Axelsen and India's 21st-ranked L...