Ronnie O'Sullivan and Mark Selby tumbled out of the Welsh Open while defending champion John Higgins prevailed in a final frame decider to reach the quarter-finals.

O'Sullivan was overwhelming favourite when he clinched the opening frame of his third round encounter against Alexander Ursenbacher courtesy of a 118 break - the 994th century of a glittering career.

The five-time world champion established a 2-1 advantage only for his unheralded Swiss opponent to reel off the next three frames for a shock 4-2 victory.

A magnanimous O'Sullivan told "The better man won on the day. He potted some great balls and played with freedom and abandonment which is a fantastic way to approach any game.

"I've got nothing but praise for him, he's great to watch. I had fun out there and gave it my best shot."

Ursenbacher, ranked 71st in the world, had never previously progressed beyond the last 64 of a ranking event but his journey was halted in the fourth round later on Thursday as he was beaten 4-2 by China's Zhao Xintong.

Noppon Saengkham, a semi-finalist here last year, registered the second 147 break of the week but was brushed aside 4-1 in his third round encounter against Selby, who then succumbed to an upset defeat in the last 16.

The world number one made a break of 135 as he moved 2-1 ahead of Hossein Vafaei but the Iranian rallied.

Selby moved 58-12 clear in the seventh and final frame but Vafaei was not overwhelmed and a break of 54 saw him clinch a stunning 4-3 win.

Higgins, meanwhile, was pushed all the way by Jack Lisowski, who three times came back from a frame down before losing 4-3.

Lisowski had two chances to secure victory in the decider and led 40-1 at one point, only for Higgins, chasing a sixth title, to hold his nerve with a 71 clearance.

The Scot will next take on Joe O'Connor, who saw off world number eight Ding Junhui 4-1 to reach the last eight.

Former world champion Neil Robertson - who registered the week's first maximum 147 on Tuesday - continued his impressive run as he needed only 53 minutes to dispose of Michael Georgiou 4-0.

The Australian left-hander will next take on Kurt Maflin, who defeated Elliot Slessor 4-2.

Scott Donaldson will face Vafaei after overcoming Ian Burns 4-2 while Stuart Bingham set up a clash with Xintong by defeating Robbie Williams by the same scoreline.