RONNIE O'Sullivan is at a loss as he seeks to stay on track in the PowerHouse UK Snooker Championship in York tonight.

Although the defending champion beat Hong Kong's Marco Fu 9-7 last night at the Barbican Centre to reach the last eight, 'The Rocket' is suffering an alarming dip in form.

His positional play has gone to pot this week. Out of sorts in his opening match victory on Saturday and in the first half of his third round duel with Fu, things did not get any better yesterday evening.

Leading 5-3 overnight he lost the first two frames yesterday and although he won the next three to lead 8-5 there were no signs of the smooth, flowing play for which he is renowned. Fu fought back with a 101 break to win the 14th frame and took the next before O'Sullivan made sure of a place in the quarter-finals.

"I know I have not been playing well, everyone knows that. I know I have to improve," O'Sullivan readily admitted afterwards. "But unless something drastic happens in the next 24 hours I am struggling. It is in there somewhere. I cannot put my finger on it, whether it's timing or whatever.

"I am not lacking confidence. I am delighted with my results.

"It can't get worse. At least I hope not," he added.

His quarter-final against Drew Henry started this afternoon and is will be played to a finish tonight. The winner will meet either Ken Doherty or John Higgins in Friday's semi-final.

Higgins brought the impressive run of Steve Davis to an end last night, beating the six-times world champion 9-7.

"He played fantastic, every credit to him," said former world and UK champion Higgins. "But I played very well too. He is playing better than a lot of those in the top 16. His control is superb."

Looking ahead to his quarter-final against Doherty, which started this afternoon and will finish tonight, Higgins said: "Ken is a battler. He can scrap it out with anyone. And he is a better break-builder than Stephen Hendry and Ronnie O'Sullivan."

Davis, who was annoyed that he threw away a winning chance in the last frame which would have kept him in the match, said that while at the end of the day he lost he showed that he was able to get one of the game's top players on the back foot and to make him think harder.

"I need a few more matches like that to re-learn how to play at the top level. I am a step closer to it than I was a year ago. And I am really enjoying the challenge."

World champion Peter Ebdon had little difficulty beating Alan MacManus 9-2 to get through to a quarter-final match tomorrow against world No 33 Robert Milkins.

Mark Williams was untroubled in defeating Chris Small 9-3 to complete the quarter-final line-up. He takes on Stephen Hendry tomorrow knowing that the Scot is out for revenge, having lost 9-8 to Williams in an epic duel last year after Hendry had led 8-4.

Tomorrow's matches:

Quarter-finals (1pm and 6.45pm): Mark Williams v Stephen Hendry, Robert Milkins v Peter Ebdon.

Updated: 11:39 Wednesday, December 11, 2002