China's Ding Junhui beat Scotland's former world champion John Higgins to move into the last eight of the Northern Ireland Trophy.
China's Ding won last year's UK Championship
Ding prevailed 5-3 to set up a clash with Ireland's Ken Doherty, who edged past Scot Stephen Maguire 5-4.
England's Stephen Lee defeated seven-time world champion Stephen Hendry of Scotland 5-4.
Lee will now play 2005 world champion Shaun Murphy, who beat Australia's Neil Robertson by the same scoreline.
Higgins was never in front against last season's UK Champion Ding, also winner of the 2005 China Open.
He had breaks of 40 and 53, but never reproduced the sparkling form which won him two titles last season as Ding wrapped up a memorable victory with runs of 68, 54, 75 and 87.
Earlier, world champion Graeme Dott battled back to beat Leicester's Mark Selby 5-4.
Selby, this summer's World 8-Ball champion, forged 3-1 ahead with breaks of 107 and 89.
My game is about having fun - and I had fun out there
But world number four Dott responded with runs of 68, 96 and a superb 109 to claim a final frame win.
"To be honest I thought there was no way I was going to win it," admitted Dott.
"It's great to be in the quarter-finals. Other than a couple of scrappy frames I'm playing really, really well."
Dott now faces Dominic Dale, who ground out a 5-4 win against Gerard Greene.
Ronnie O'Sullivan eased to a 5-2 win over Matthew Stevens and his next opponent, Ryan Day, beat Mark Williams by the same scoreline.
Two-time world champion O'Sullivan sunk breaks of 46, 48, 49, 40 and 44 to fight back from 2-1 down to lead 4-2.
The Chigwell potter then knocked in runs of 71 and 103 in the last two frames to make sure he progressed.
"My game is about having fun - and I had fun out there," he added. "I'd been much happier having a barbecue than having a long slog of a match."
Day also impressed, knocking out good friend and practice partner Williams.
The Bridgend player pocketed breaks of 99, 60, 79, 72 and 49, while last year's China Open winner Williams managed a high break of just 47 on the way to suffering a 5-2 defeat.
Dale also had to fight hard to beat Ulsterman Greene, the last local hope left in this year's tournament.
"I knew Gerard would be a tough match, but I was solid and my safety was good," said Dale.