Kyren Wilson crashed out of the Northern Ireland Open following a 4-2 defeat by Mitchell Mann in the third round on Wednesday.
The world number five is the highest-profile casualty in Belfast so far this week.
Wilson reached the semi-finals in the inaugural event at the Waterfront Hall in 2016.
However, the Warrior came unstuck at the hands of the world number 109, who made breaks of 92 and 68 on the way to a morale-boosting win.
Mann subsequently claimed his second successive victory over Wilson, having also prevailed 6-2 when the players met in the opening round of the UK Championship five years ago.
Meanwhile, Shaun Murphy and Stuart Bingham narrowly avoided joining Wilson at the exit door; overturning 3-2 deficits to advance in deciding frames against Tian Pengfei and Ashley Carty respectively.
Mark Williams also produced an inspired turnaround against Jak Jones. Despite an ongoing struggle with gout, the 2017 champion produced back-to-back centuries of 102 and 100 from 2-0 down against his compatriot, before further runs of 53 and 72 sealed a 4-2 win.
There were no such problems for Ronnie O’Sullivan; the three-time Northern Ireland Open finalist running out a comfortable 4-1 winner over Alfie Burden, while World champion Mark Selby overcame Gary Wilson by the same scoreline.
Contributions of 58, 52 and 83 were enough to see reigning champion Judd Trump past Lu Ning 4-2, as Masters winner Yan Bingtao thrashed Oliver Lines 4-0.
Elsewhere, John Higgins hit three centuries in his 4-2 victory over Luca Brecel, while Championship League winner David Gilbert had two tons as he beat Louis Heathcote by the same scoreline.
Northern Ireland Open 2021 Results
Wednesday October 13
Liam Highfield 4-1 Ryan Day
Chris Wakelin 2-4 Tian Pengfei
Rory McLeod 0-4 Gary Wilson
Mark King 1-4 Lyu Haotian
Kyren Wilson 2-4 Mitchell Mann
John Higgins 4-2 Luca Brecel
Ronnie O’Sullivan 4-1 Alfie Burden
Yan Bingtao 4-0 Oliver Lines
Mark Williams 4-2 Jak Jones
Jimmy Robertson 4-0 James Cahill
Stuart Bingham 4-3 Ashley Carty
Mark Selby 4-1 Gary Wilson
Judd Trump 4-2 Lu Ning
Shaun Murphy 4-3 Tian Pengfei
David Gilbert 4-2 Louis Heathcote