World champion Mark Selby suffered a shock first-round exit to world number 69 Lee Walker at the Yushan World Open.
Walker won 5-2 against world number one Selby, who missed the start of the season with a broken toe.
Selby won his third World Championship in May but has not gone beyond the last 16 of any tournament this season.
Shaun Murphy, the 2005 world champion, is also out after losing 5-3 to Daniel Wells, and Ding Junhui beat fellow Chinese player Zhang Anda 5-3.
Walker will face Robert Milkins in the second round, Wells takes on Luca Brecel and Ding faces Xiao Guodong.
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