Mark Selby crashed out of the Welsh Open in the second round as the world champion was beaten by Liam Highfield in Newport.
Having been 2-0 down, world number one Selby battled back and secured a 3-2 lead with a break of 115 before Highfield took the next two to triumph 4-3, wrapping things up with a 92 clearance.
Highfield, the world number 40 who will now face Michael White, said in an interview on World Snooker Tour's official Twitter feed: "The way I handled it was my most pleasing thing. I stayed calm throughout the match and took my chances and made it difficult for Mark.
"I do think the key with Mark is to stay patient, but it is very hard because my natural instinct is to attack and be ultra-aggressive and play that way. I think the key is to just err on the side of a little bit more caution.
"I held myself together really well towards the end, just a good break, and I think I played the balls in the right order and the right shots at the right times. Just onwards and upwards, try to get a run here."
Fergal O'Brien's tournament came to an end with a 4-2 defeat to England's Jimmy Robertson. The Dubliner was 1-0 and 2-1 ahead but the world no 27 rattled off the last three frames to advance.
There were also exits for Zhao Xintong and Stuart Bingham, who suffered 4-3 defeats to Jak Jones and Elliot Slessor respectively.
Ronnie O’Sullivan made safe progress to the next round as he saw off Lukas Kleckers 4-2.
Wednesday’s early session also included Kyren Wilson beating Li Hang 4-0, Barry Hawkins getting past Ashley Carty 4-1, Shaun Murphy winning 4-1 against Anthony Hamilton and Yan Bingtao defeating Zhao Jianbo 4-0.
Mark Allen is in action against Joe Perry tonight.