SHEFFIELD (England), April 25: World number one Ronnie O'Sullivan came from behind to beat qualifier Ryan Day on Monday and complete the world championship quarterfinal lineup.

O'Sullivan trailed 9-7 at the start of the final session but took advantage of some costly errors from Day to win six out of seven frames and seal victory.

“It was a tough game and I'm lucky to be through,” O'Sullivan said at the post-match news conference. “He had his chances to win, but he wasn't able to finish me off.”

Briton O'Sullivan, a twice winner, is now looking forward to a last eight clash with another twice former champion, Mark Williams.

“I need to raise my game a little because he's playing well again,” O'Sullivan said.

Ireland's Ken Doherty beat Matthew Stevens 13-8 to set-up a quarterfinal meeting with Hong Kong qualifier Marco Fu.

“Marco played very well against Stephen Maguire and anyone who's in the quarterfinals has a chance of winning the tournament,” said Doherty.

Peter Ebdon, who secured his place in the last eight with a comprehensive 13-2 victory over David Gray, will now face defending champion Shaun Murphy.

“He's been an exceptional champion and all credit to him for doing so much to promote snooker,” Ebdon told reporters.

Scotland's Graeme Dott will face Australian qualifier Neil Robertson after completing a 13-9 win over Nigel Bond.

“Neil is a great player and I think it'll be a pretty even match,” said Dott.

Monday’s results:

Second round (best of 25 frames):

Ronnie O'Sullivan (England) beat Ryan Day (Wales) 13-10 (77-41, 88-5, 4-75, 33-66, 5-86, 140-0, 0-69, 105-28, 92-22, 98-13, 1-58, 19-104, 0-80, 114-36, 61-70, 36-69, 75-59, 76-60, 69-30, 100-0, 103-31, 50-63, 75-10); Peter Ebdon (England) beat David Gray (England) 13-2 (107-12, 68-39, 30-69, 67-16, 82-25, 59-65, 72-8, 63-0, 76-69, 59-33, 82-38, 76-53, 78-5, 65-22, 70-45); Ken Doherty (Ireland) beat Matthew Stevens (Wales) 13-8 (37-75, 66-41, 65-57, 88-11, 18-58, 0-89, 76-0, 5-82, 79-48, 56-48, 68-55, 0-74, 43-69, 0-95, 83-7, 55-62, 84-6, 75-43, 71-27, 136-0, 74-2); Graeme Dott (Scotland) beat Nigel Bond (England) 13-9 (69-33, 91-11, 26-64, 11-94, 62-53, 114-9, 77-27, 15-64, 51-54, 65-7, 0-68, 69-42, 0-111, 63-51, 68-7, 88-4, 66-48, 0-127, 61-64, 89-9, 0-75, 60-19). —Reuters