John Higgins saw the defence of his Welsh Open title end at the fourth-round stage as he was beaten by Michael White in Cardiff.
The four-time world champion went down 4-1 to the Welshman, who advances to a quarter-final against world number nine Mark Allen.
Antrim man Allen claimed his place in the last eight with a 4-3 victory over Barry Hawkins, while world number three Neil Robertson saw off Marco Fu 4-2 and Ben Woollaston beat Martin Gould 4-1.
Didn't score as well today but potted them when it mattered. Another good win. Hopefully three more to go #WelshOpen— Mark Allen (@pistol147) February 18, 2016
Ronnie O'Sullivan eased through to the last eight as he overcame China's Yu Delu 4-1.
Delu took the first frame as he fluked a respotted black, but O'Sullivan powered back to take victory.
O'Sullivan said on BBC Sport: "Yu Delu is a brilliant player, so I was a bit nervous at the start.
"I maybe was giving him a little bit too much respect. I lost the first frame, but got some momentum going after."
O'Sullivan will now play world number one Mark Selby, who saw off another Welshman in former world champion Mark Williams 4-2.
World number six Judd Trump suffered an agonising 4-3 defeat to Joe Perry after missing the potential match-winning black in the sixth frame.
His slip-up allowed Perry to level the match and then go on to take victory in the deciding frame.
Ding Junhui wrapped up the day's action by beating Luca Brecel 4-2.