BIRMINGHAM, England (REUTERS) - World champion Chen Long avoided a potential first-round exit at the All-England Championships on Wednesday and blamed an uncomfortable pillow for a sluggish start to his campaign.

Chen, the world No. 1 and top seed, woke up with a muscle spasm in his neck, putting the issue down to a soft hotel pillow.

He had worn a plaster to ease a sore neck and his uncomfortable night's sleep nearly proved his undoing as fellow countryman Xue Song raced away with the first game 21-12.

A shock upset looked on the cards as Chen stretched tiredly to net at 16-16 in the second before the 2013 champion rattled off three points in a row to set up a decider.

Chen's forehand smash was prominent thereafter and he comfortably took the third 21-9, setting up a last-16 clash with Hsu Jen Hao of Chinese Taipei.

"I started really slow and I wasn't in the best of form out there," Chen told reporters.

"I needed to play quick and attack more, play rally-to-rally and not think about the result. I kept my consistency and tried to control him by not doing anything too risky."

Chen's female compatriot Li Xuerui, also world No. 1, had earlier stepped through the gears in her opening match.

Olympic champion Li eased past Beiwen Zhang of the United States 21-13 21-17 and said the multi-million pound redesign at the Barclaycard Arena had played a major part in her victory.

"The whole arena has been refurbished and it is a big change," Li said after her 33-minute win.

"The most important thing is the lights overhead as in previous years it has been too bright."

Li was surprisingly beaten in a first-round upset in 2013 - 12 months after winning the title for the first time - but it was a composed Chinese who set up a second-round clash with compatriot Sun Yu.

Korean Lee Dong Keun lost one of the longest male singles matches in recent memory against Germany's Marc Zwiebler.

The German, who reached the All-England semi-finals in 2011, outlasted Lee 21-17 19-21 21-19 over an energy-sapping 96 minutes.