Defending champion Ronnie 'Rocket' O'Sullivanproduced some world class snooker to come from behind and reach the WorldChampionship quarter-finals with a 13 frames to 11 victory over Joe Perry onSaturday. The 38-year-old Englishman -- bidding for a sixth world title at the Crucible Theatrein Sheffield, England -- had trailed 9-7 overnight and having shared the openingfour frames of the final session O'Sullivan was just two frames from defeat.However, suddenly the mercurial cuesman -- whose brilliance has been offset byregular clashes with the sport's authorities -- found his touch and barely allowedPerry a look-in.Breaks of 53 and then 52 were enough to level the match and then he upped the antewith a wonderful break of 124 to take the lead in the match for the first time.Perry's spark had completely gone and a loose safety shot by the 39-year-oldEnglishman in the 24th frame gave O'Sullivan his chance and he took it in stylefiring off a break of 113 to round off a remarkable sequence of frames.O'Sullivan will play either Rickey Walden or another Englishman Barry Hawkins inthe last eight.The Walden and Hawkins match, a rematch of last year's semi-final which the latterwon, will resume later on Saturday with Walden leading 9-7. Source: AFP