The former UK champion, who also failed to clear the opening hurdle in the recent Thailand Classic, crashed out 5-2 to Portadown's Michael Duffy in the biggest upset of the season so far.
"It's a big disappointment because I have been working really hard on my game and practising more than I have in a very long time," said the world No 3 from Essex, whose well-documented family problems appear to be having an adverse effect on him.
O'Sullivan, taking on some risky pots which Duffy described as "mad", fell 2-1 behind and also trailed 36-0 in the fourth frame before briefly coming to life. The 19-year-old constructed a superb 102 clearance to draw level at 2-2 and it looked like he had weathered the storm.
But Duffy, whose only other significant achievement in three years as a professional was to record a victory over Alex Higgins, regained the lead by winning the scrappy fifth frame on the blue. After that, Duffy pulled away with breaks of 35 and 43.
"Ronnie played well in patches, but he didn't seem to be concentrating 100 per cent, and you could tell he wasn't totally with it," Duffy said.
Duffy goes forward to meet fellow Ulsterman Joe Swail, who maintained his solid start to the season by beating Scunthorpe's Jeff Cundy 5-3.
For the second day in a row, a player from Grimsby left the table visibly upset with his opponent. On Tuesday, Mike Hallett was annoyed about a free-ball decision during the deciding frame of his 5-4 defeat by Neal Foulds. Yesterday, it was Dean Reynolds who expressed disgust at the slow play of Mark Flowerdew, who finally beat him 5-3 after a 4hr 21min marathon.
"It was ridiculous," Reynolds said. "Referees should do something about the speed of play and intervene. Throughout my career I have never come across a slower player than him. It was a joke and it didn't do the game any favours."
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