Hossein Vafaei beat world number one Mark Selby to complete the Welsh Open quarter-finals octet late on Thursday in Cardiff.
The Iranian’s gutsy 54 clearance in the decider consigned Selby to another early exit in a Home Nations event and concluded another day at the Motorpoint Arena that was full of upsets.
Ronnie O’Sullivan, Ding Junhui, Mark Allen, and Barry Hawkins all bowed out to leave just three seeded competitors in the hunt.
The trio each understands what it takes to capture glory in Wales having prevailed in the third oldest ranking event in the past, but such has been the randomness of this edition that nothing is guaranteed.
Defending champion John Higgins is among the few marquee names who are still in contention for the £70,000 top prize.
The Scot has been struggling with form, motivation, and confidence recently but has a love affair with this tournament having emerged triumphantly a record five times.
On a busy fourth day of action in which two rounds took place, Higgins edged Craig Steadman and Jack Lisowski to set up a Welsh Open quarter-finals tie with Joe O’Connor.
The latter will be embarking on unknown ground, with his surprise 4-1 defeat of Ding in the last 16 helping him to reach this stage of a ranking event for the first time in his career.
O’Connor, the 2018 English amateur champion and enjoying his debut campaign on the Main Tour, took advantage of his esteemed Chinese opponent’s inability to score heavily.
Higgins will be an overwhelming favourite, though, as the format increases to the best of nine frames.
Also in the top half of the Welsh Open quarter-finals draw is 2017 champion Stuart Bingham.
The 42 year-old produced a scintillating display of power scoring to come from 2-1 down and deny Robbie Williams with a hat-trick of successive century breaks.
Bingham will meet one of the most talented up-and-coming Chinese cueists in Zhao Xintong next, with a semi-final berth at stake.
Zhao dropped off the circuit at the end of last season but immediately returned via Q School and has been a transformed figure since.
The 21 year-old overcame Alexander Ursenbacher – who sensationally ousted the “Rocket” earlier in the day – to go within a victory of matching his run to the last four of the China Championship.
Bingham and Zhao have met three times in the past with the 2015 world champion triumphing on each occasion, including in the first round of last week’s World Grand Prix in Cheltenham.
In the bottom bracket, Neil Robertson represents the only proven champion as he mixes it with a trio of players ranked outside the world’s top 32.
The Australian barely survived his last 32 clash when he fought back from 3-1 behind to deny Paul Davison in a decider.
However, an improved performance in the fourth round helped the 37 year-old to inflict a whitewash scoreline on Michael Georgiou.
Kurt Maflin will be the 2007 champion’s next challenge after the Norwegian took advantage of a kinder route to reach the last eight of a ranking event for only the fifth time.
Unfortunately for Maflin, his record against Robertson is dismal with just one defeat of the Melbourne man in seven prior battles.
Vafaei, meanwhile, will bid to build on his stellar success over Selby as he takes on Scott Donaldson in his Welsh Open quarter-finals fixture.
The Iranian is a former world amateur champion at both senior and junior levels, and has long been considered as a player capable of breaking into the higher echelons.
Against Donaldson, he will hardly get a better opportunity to match his previous best run in a ranking event – a semi-final appearance in the 2017 China Open.
That said, Donaldson has never lost a quarter-final clash having gone on to reach the semi-final each time he has been to this stage in the past.
Elsewhere, Noppon Saengkham entered the history books during his 4-1 loss to Selby in the third round.
The Thai compiled his maiden 147 break in the second frame to match Neil Robertson’s feat from earlier in the week and guarantee a share of the £17,000 bonus.
Live coverage of all Welsh Open quarter-finals will be on Eurosport, Quest, and BBC Wales.
Click here to view the draw (Times: CET)