Zii Jia, the former world No 2 whose ranking dropped to No 52 during the layoff, was a pale shadow of himself, losing to world No 38 Jeon Hyeok-jin in straight games of 17-21, 11-21 in a match that lasted 41 minutes.

The Malaysian player moved around the court with utmost caution, obviously to avoid any hard landing on his feet that would cause a recurrence of his ankle injury.

This is the Korean player’s second win over the Paris Olympics bronze medallist in their five encounters so far.

Hyeok-jin will take on Japan’s Yushi Tanaka, who pulled off one of the biggest upsets of the day by beating fourth seed Li Shifeng of China 19-21, 21-11, 21-15 in another first round.

At the last World Championships in 2023, Zii Jia was knocked out in the quarter-finals. His last BWF title was at the Super 500 Australian Open last year.

In an interview with BWF on Sunday prior to the championships, Zii Jia admitted that the long lay-off was the darkest spell of his career, adding that he was not only battling the injury but also depression, loneliness and self-doubt.

His injury woes began at the World Tour Finals last December when he damaged his ankle badly just as he was about to win his last group match to enter the quarter-finals.

Since then, he has played two tournaments — the Orleans Open and the All England, both in March — before being forced to skip all tournaments after that to recover.