Rocket Ronnie loses to Mark Allen in Masters

Allen capitalised on some lackadaisical O'Sullivan snooker to lead 4-2, before the crowd favourite fought back to draw level at 4-4 at Wembley Arena.

Allen, 24, held his nerve with a superb clearance of 87 to edge ahead again and he took a scrappy 10th frame to win it.

"I had great support but you've got to do the business on the table," world number nine O'Sullivan told BBC Sport.

Allen, the world number 11, told BBC Sport: "He did miss a few but he's only human - people expect 147s all the time from him but you can't do it.

"He's a genius and he will continue to be a genius as long as he wants."

The 'Rocket' follows defending champion Mark Selby, former world champion John Higgins and world number three Mark Williams in making an early exit from the tournament.

It is only the second time since his debut in 1994 that the Essex-based player has lost in the first round.

O'Sullivan, who also lost in his first match at the UK Championships, admitted before the start he felt under pressure to perform with so much local support at Wembley.

But the 35-year-old never approached anything like his fluent best as Allen, who reached the semi-finals at last year's World Championship, took advantage to reach the quarter-finals.

"All credit to Mark," O'Sullivan told BBC Sport. "He played a strong game and put me under pressure.

"He's had a good season so I was up against it. I missed a few balls. I'm not concerned about my form - obviously it's disappointing to lose in two big tournaments early in the season."

After exchanging the first two frames O'Sullivan bizarrely conceded the third when only needing one snooker and to pot the final four balls to get back on terms.

The 1995, 2005, 2007 and 2009 champion seemed distracted and unable to go a whole frame without making a mistake and Allen - not at his best either - was soon 3-1 up.

That should have been 4-1 only for the 24-year-old to let O'Sullivan back in to take the fifth frame, but more poor safety from the usually reliable Englishman allowed Allen in again for 4-2.

Allen, yet to win a ranking title, could not hide his nerves as he gifted his more illustrious opponent the next two frames, but he showed formidable focus to hit back with a stunning clearance to move within one frame of victory.

O'Sullivan tried to rally, but a succession of missed pots ended with Allen slotting a red down the left-hand cushion and he kept his cool to earn one of the most important wins of his career.

"There wasn't any quality so much as bottle, I've shown that over the last few years," added Allen.

"He put me under a lot of pressure from 4-2, his long potting was phenomenal, but if somebody had given me 4-4 at the start I would have taken it - it's best of three from there and I'm capable of beating Ronnie.

"There's no reason not to go on and win it now, I just have to get in that mindset all the time."

In the last eight, the left-hander will face either Stephen Hendry or world champion Neil Robertson, who meet on Wednesday.

Meanwhile, Marco Fu survived a typically gritty fightback from Stephen Maguire to book his place in the quarter-finals against Peter Ebdon with a titanic 6-4 win.

The Hong Kong cueman, ranked 16, edged ahead 2-1 after three scrappy frames but then knocked in a break of 109 to be in control at the interval.

A 117 break then extended his lead to 4-1 and he then got within one of victory to leave the 29-year-old Scot on the brink.

But Maguire, who has reached the Masters semi-finals three times in the last four years, roared back with breaks of 46, 53, 74 and a stunning 142 - the tournament's highest so far - to get back to 5-4.

The sixth seed had chances to take it to a last-frame decider but Fu battled his way through an epic 46-minute frame to secure only his second last-eight spot in the tournament.