Lee, who has settled for silver at the last three world championships, blew away Zwiebler 21-14, 17-21, 21-8 to book a spot in the third round.

Lee only returned to the badminton circuit in May after being slapped with a ban for doping, and enters the world championships unseeded for the first time in years.

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But his clinical dismissal of Zwiebler, capped off with a string of unanswered smashes in the third set, has the Malaysian looking top of his game and hungry for his maiden crown.

Zwiebler, who is close friends with Lee, said the Malaysian had clearly returned to former glory during his eight-month hiatus and was the "best player" in the field to take on the Chinese juggernauts Chen Long and Lin Dan.

"He is an almost perfect player. He doesn't have a weak spot," he told reporters.

"If he is ready to put away the pressure, and focus on his strengths, then definitely he can be champion."

World number one Chen's bid to defend his world crown got off to a strong start Wednesday, as he dismissed Estonia's Raul Must 21-15, 21-7.

The top seed is expected to encounter little trouble until the quarter-finals, where he will likely face seventh-seeded Dane Viktor Axelsen.

Chen, who has already won four titles this season, wasn't getting ahead of himself, however, and stressed he would take one match at a time.

"Today there are many good players. They could all win," the 26-year-old told reporters.

It seems a wise approach from the defending champion, who has faltered early in other tournaments this year against lesser-ranked opponents.

Five-time world champion Lin marched onward in his campaign for a sixth crown, brushing aside 75th-ranked Daniel Paiola 21-14, 21-14.

But the fifth seed and two-time Olympic champion was surprised at the resistance he encountered playing the unseeded Brazilian, suggesting he was feeling his age.

"My physical condition is not like it used to be," the 31-year-old told reporters.

"I did not think my opponent would be so difficult."

There were upsets elsewhere, with local hero Tommy Sugiarto unable to fend off wily Hong Kong shuttler Wei Nan in a gripping three-set contest.

Sugiarto, Indonesia's only hope in the men's singles, came within an inch of winning the epic 70 minute battle but eventually succumbed 26-24, 8-21, 22-20 to his unseeded opponent.

The 15th seed narrowly dropped the first set before steamrolling Wei in the second. But the real fireworks were in the decider, with the pair neck and neck as the crowd rallied before the home favorite.

"It is hard to accept this defeat," the 27-year-old told reporters after the match.

It wasn't all bad news for the hosts on Wednesday, with local shuttler Lindaweni Fanetri upstaging 13th seed Minatsu Mitani from Japan in the women's singles.

Back in the men's game, unseeded Vietnamese Nguyen Tien Minh also ejected 10th seed Indian Kashyap Parupalli 17-21, 21-13, 21-18.

Indian H.S. Prannoy, the 11th seed, was more fortunate, taking a place in the last 16 with a routine victory over Uganda's Edwin Ekiring 21-14, 21-19.

He will face Axelsen on Thursday, a match the Dane is approaching warily.

"He's a tricky player," Axelsen said of his Indian opponent.

World number two Jan O. Jorgensen will face ninth-seeded South Korean Son Wan Ho in the third round on Thursday, while women's second seed Saina Nehwal must see off 14th seed Sayaka Takahashi of Japan. (++++)

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