Lee Chong Wei's participation at the 2018 BWF World Championship in Nanjing, China, is suddenly in doubt.

The Malaysian shuttler, who would face Brice Leverdez in the first round, failed to show up for training at the Academy Badminton Malaysia in Bukit Jalil for the past week.

His absence raised suspicions of an injury, but there was no official confirmation from the Badminton Association of Malaysia (BAM) whether or not he would withdraw from the World Championships, especially with the 2018 Asian Games on the horizon.

When asked by the media, national men's head coach Misbun Sidek said he was aware that Lee requested for a break after the Malaysian Open and Indonesian Open but did not expect him to be away for longer than expected.

"It is out of the ordinary. He previously rested for a long period once, which was for his muscle recovery process," Misbun commented on his absence.

"From what I can see, he does not want to be disturbed and just wants to rest.

"I suggest we wait for the BAM to make an announcement, if any. Maybe he has a lot of leave days remaining, so let's just let him rest."