Video - O'Sullivan wins tense deciding frame
Ronnie O'Sullivan remains on course for his fifth Masters title after an epic 6-5 semi-final win over Mark Williams.
The Welshman opened with a 107 break and went 2-0 up before runs of 86 and 99 from O'Sullivan levelled matters.
The pair then matched one another frame for frame. O'Sullivan went 3-2 up but a superb 132 break drew Williams level and the next two frames were shared.
A 96 break put Williams 5-4 up but 67 from O'Sullivan forced a decider. Both had chances before The Rocket took it.
"I don't know how I won that to be honest," O'Sullivan, who reached a record-equalling ninth Masters final, and his sixth in the last seven years, told BBC Sport.
O'Sullivan 'surprised' to win epic
"At the start I expected to lose quite comfortably, because I know Mark's ability. But I played a few left-handed shots and remembered how it felt to be like a snooker player.
"The things I had to go through out there...I was willing the balls to go in, but I didn't know what I was doing from one shot to the next. I am just relieved to go through.
"Mark has been struggling for a while but when you see him cueing like that, you know it is only a matter of time before he starts doing well again.
"He is scoring well and if he plays like that he is a danger at the World Championships.
"He is a competitor and he was the better player on the day by far - I was just hoping to make a game of it. I thought I was going get a good hiding."
Earlier this week O'Sullivan was labelled "miserable" at the table by new World Snooker chairman Barry Hearn, but he revealed his demeanour was down to a lack of confidence.
"The reason I don't like smiling is because I'm so unconfident when I go out there," he added. "I just don't expect to play well these days.
"I'm petrified going up the tunnel sometimes as I'm worried I'll make a fool of myself and not give my opponent a game.
"But once you get pushed about a bit by your opponent, your survival instinct kicks in. But I keep having to find something, and that is really hard."
O'Sullivan, who equals Stephen Hendry's record of nine Masters finals, has won four of his previous eight - in 1995, 2005, 2007 and 2009. He lost in the finals of 1996, 1997, 2004 and 2006.
Victory on Sunday would take him to within one of Hendry's record haul of six titles, the Scot winning five in a row from 1989 to 1993 before his last Wembley victory in 1996.