Ronnie O'Sullivan dumped out of Masters

Allen had dominated the early exchanges, leading 3-1 at the mid-session interval but O'Sullivan, currently down at number nine in the world rankings, fought his way back to 4-4.

The Northern Ireland potter recovered his poise, though, and came through to set up a clash with either Stephen Hendry or world champion Neil Robertson.

Allen took the opening frame with breaks of 38 and 32 and was handed a chance in the second when O'Sullivan missed an easy black. He was unable to capitalise, though, and 'The Rocket' levelled.

That inexplicable miss set a pattern in motion, though, and he missed two more routine blacks as he went in 3-1 down at the interval. Allen was looking in imperious form and was unlucky not to record a century in frame four as he missed the brown on 88.

A break of 64 saw O'Sullivan snatch the first frame after the interval from 62-0 down, however, and brought him back within one frame.

Allen extended his lead in the next but was looking less fluent and failed to punish another error in frame seven. O'Sullivan jawed a rash double but Allen missed the subsequent red and O'Sullivan cleared nervelessly to pull back to 4-3 down.

A superb opening red in the next set up a break of 66 before he missed a tricky red to the middle, but he nevertheless levelled and set up a best-of-three finish.

The three-times world champion's problems returned in the next frame, though, as he missed an easy red and Allen took the frame with a break of 87 to the pink.

O'Sullivan led 34-32 in the next before both players struggled on the same red. Allen, though, produced an excellent long pot and cleared to the final blue to win frame and match.

The world number 11 told BBC Sport afterwards: "There wasn't any quality so much as bottle, I've shown that over the last few years.

"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. He wasn't at his best but I'm happy to win."

O'Sullivan added: "It was a tough match, all credit to Mark. He's had a great season, got to the semi-finals of the UK and the World (Championships) and he's a big-time player.

"I had great support but you've got to make sure you do the business on the table."