Ronnie O'Sullivan admitted he had put Liverpool's Barclays Premier League title quest ahead of his own needs after battling his way into the quarter-finals of the Dafabet World Snooker Championship, while Ken Doherty's challenge was ended when he was beaten 13-8 by Alan McManus.

The defending champion turned on the power to beat Joe Perry 13-11 after flirting with defeat for much of the match.

He later revealed he had benefited from a chat with renowned psychologist Dr Steve Peters after telling him not to travel to Sheffield earlier in the week so he could concentrate on his work with Brendan Rodgers' men.

O'Sullivan told BBC Sport: "Obviously Liverpool are going for the Premier League and I know how important that is for him and for the Liverpool people.

"I have got friends from Liverpool and it would be so great if they can do it, so I'm mindful that I don't want to take all his time up.

"I said, 'That's more important, I'm going to be okay', but really I made a mistake. I could have done with him here on Thursday.

"But he said he's not going to make that mistake again, he's going to be around a bit more now."

O'Sullivan, who trailed 7-9 overnight and 9-11 at the mid-session interval, rattled off four successive frames as he hit top form to book his place in the last eight.

O'Sullivan never led in the match until he claimed the penultimate frame with a break of 124, but once in front he took full advantage, sealing victory with another of 113.

He won the first frame of the session and, after Perry had re-established his two-frame lead in the next with O'Sullivan calling a foul on himself, compiled a break of 82 to stay in touch.

Perry refused to wilt and eased himself to within two frames of victory by claiming the 20th, but O'Sullivan clinched the next two with breaks of 53 and 52 before turning on the style to take himself over the finishing line.

Perry said: "I have got no regrets over anything I did. I was fully committed to every shot I played, I still felt calm and relaxed at the end, so I did everything I could.

"I just ran into an absolute genius at the end, so what can you do?"

O'Sullivan will face either Shaun Murphy or Marco Fu in the quarter-finals, while McManus will tackle Mark Selby after seeing off fellow veteran Doherty.

Leading 4-3 overnight, McManus claimed the first six frames of the morning session to take himself to within three of victory before Doherty stemmed the tide with breaks of 93 and 88.

He took the momentum from those two frames into the evening session, winning three of the four frames before the interval to trail only 11-8, but McManus extended his lead once more in frame 20 and wrapped up victory with a break of 83.

Barry Hawkins is through as well after repeating his win over Ricky Walden in last year's semi-final.

Walden had led 9-5 but Hawkins took the final two frames of Friday's play and kicked off Saturday with a 104 break, winning three of the first four frames to level the match.

He edged ahead at 11-10 - the first time he had led since winning the opening three frames - and though Walden hit back with a 53, Hawkins went ahead once more and wrapped up victory with a 61 break.

Judd Trump, the former world number one and a semi-finalist last year, reeled off four straight frames to finish the first session with a 6-2 lead over Ryan Day.

The 24-year-old was twice pegged back by Day after leading 1-0 and then 2-1 before pulling clear as he started to hit form.

Trump took the fifth frame by a single point but runs of 76 in the next and 78 in the eighth saw him establish a four-frame advantage.

The Bristol cueman outscored his opponent by 230 points to 14 in those final three frames.

Dominic Dale led Michael Wasley 7-1 after a one-sided first session to their match.

World number 73 Wasley marked his Crucible debut with a stunning upset of Ding Junhui in the first round but was unable to repeat that display, despite a 66 to win frame two.

Dale, who led Mark Davis 7-2 after the opening session of their first-round clash, started in similarly impressive style aided by breaks of 74, 75, 59 and a closing 106.