Sullivan says he feels an underdog despite his win

O'Sullivan made breaks of 90, 56, 94 and 100 on his way to a 5-1 victory in Brighton.

But, with his main rivals also on top form, the world number three admitted he was finding it tough on the green baize.

"I feel like I'm scrapping for my life," he said. "I'm an underdog - I'm kicking around looking for results.

Stephen Hendry advanced to the next round with a 5-0 defeat of Joe Perry.

Higgins makes history

And, despite, failing to make a maximum clearance for his third-straight match, John Higgins eased past Sussex pro Mark Davis 5-2.

Mark Williams, who last month won the LG Cup crown to go with the UK, Masters and world crowns, is safely through after beating Fergal O'Brien 5-2.

You have to put in the work if you want to beat these guys but I've been lazy Ronnie O'Sullivan

"John is back in form and he's probably got the best all round game. He's like the Rolls-Royce of snooker," O'Sullivan added.

"And Mark is obviously playing well at the moment, so I'm just hoping to compete.

"You have to put in the work if you want to beat these guys but I've been lazy."

O'Sullivan, who was beaten 5-0 by Matthew Stevens in the last 16 of the LG Cup, now faces Northern Irishman Gerard Greene.

The Kent-based player reached the quarter-finals of a major tournament for the third time in his career by beating compatriot Joe Swail 5-1.

Greene lost the opening frame but made breaks of 80 and 51 to lead 2-1, added the next two and then made a 30 clearance to steal the sixth for victory.

Matthew Stevens completed the quarter final line-up thanks to a 5-3 win over Peter Ebdon.