Jordan Brown's defence of his Welsh Open crown was ended at the first hurdle after he went down to a 4-3 defeat to Mitchell Mann at Celtic Manor.
Brown, who defied odds of 750-1 at the outset of last year’s tournament to collect the first ranking title of his career by beating Ronnie O’Sullivan in the decider of a gripping final, went 2-1 ahead with a 124 break.
World number 89 Mann, ranked 65 places below Brown, twice battled back to level and then prevailed in the all-important seventh frame to move into the second round, setting up a meeting with English compatriot Ben Hancorn.
Mark Allen beat Ken Doherty 4-1 in an all-Irish clash while Fergal O'Brien won the last three frames to defeat 2013 champion Stephen Maguire 4-1.
Mark Selby defeated Chen Zifan 4-1 to breeze into the last 64, where the reigning world champion will be joined by Judd Trump, Zhao Xintong, John Higgins, Stuart Bingham and Mark Williams, all of whom also won 4-1.
A break of 121 was the highlight for Neil Robertson as the Masters champion thrashed veteran Jimmy White 4-0 while Barry Hawkins hammered Switzerland’s Alexander Ursenbacher by an identical scoreline.
Kyren Wilson was pushed all the way by Dominic Dale before eventually coming out on top 4-3 and Zhang Anda edged out Anthony McGill on the same scoreline while there were also wins for Shaun Murphy, Yan Bingtao, Iulian Boiko and Elliot Slessor.