Spanish badminton star Carolina Marin vowed to get back to her dominant best after her bid for a record fourth world title was ended by Japan's Akane Yamaguchi on Friday.
Marin is feeling her way back into competition after suffering a horror knee injury last year that forced her to miss the Tokyo Olympics and kept her out of action for a year.
She returned to the court in May this year but current world number one Yamaguchi was too strong in their world championships quarter-final in Tokyo, advancing with a 21-17, 21-17 win.
Marin said she "felt quite good" physically but "made many mistakes in my strategy" as Yamaguchi wore her down in front of an expectant home crowd.
The Spaniard said she would "keep looking forward" as she tries to recover the form that made her a three-time world champion and an Olympic gold medallist at the 2016 Rio Games.
"I know that if I keep going, if I keep practising hard, I will get back to my best level," said the 29-year-old, who also missed last year's worlds in her home city of Huelva because of injury.
"It's tough to lose in a quarter-final at the worlds but this is the life and times. Sometimes we need to learn about losing."
Yamaguchi's win meant all four top seeds advanced to the semi-finals of the women's competition.
The Japanese ace will face South Korea's An Se-young, who beat China's Han Yue in a 21-14, 15-21, 22-20 thriller, while the other match between Chen Yufei and Tai Tzu-ying will be a re-run of last year's Olympic final.
China's Chen, who won gold last year in Tokyo, beat Canada's Michelle Li 21-18, 21-17, while Taiwan's Tai advanced with a 21-16, 21-9 win over Thailand's Busanan Ongbamrungphan.
- Loh bows out -
On the men's side, Singapore's defending champion Loh Kean Yew said he would try to "improve everything" after his reign ended with a 21-12, 17-21, 21-8 loss to Thailand's Kunlavut Vitidsarn.
Number eight seed Loh said he struggled to cope with the drift inside Tokyo Metropolitan Gymnasium but vowed to return stronger.
"Everything I am good at, I need to become better -- whatever I'm not so good at, I need to improve that as well," he said.
Rising star Vitidsarn will face China's Zhao Junpeng in the semi-finals after the unseeded 26-year-old beat India's H.S. Prannoy 19-21, 21-6, 21-18.
Zhao lost in the quarter-finals at last year's world championships and he was happy to go one better this time around.
"I think I did a lot better in my training and also mentally," said Zhao, who stunned Malaysia's highly fancied number five seed Lee Zii Jia in the previous round.
Taiwanese number four seed Chou Tien-chen will face hot favourite Viktor Axelsen in the other semi-final after fighting off five match points to beat Indonesia's Jonatan Christie 14-21, 21-11, 22-20.
Axelsen continued his run of winning every match in straight games with a dominant 21-10, 21-10 victory over Indonesia's Anthony Sinisuka Ginting.
"I wanted to play a perfect game plan," said world number one Axelsen.
"I wanted to do my absolute best on each side of the court and I managed to do so. I was fully focused in there today."