Eurosport pundit Foulds feels O'Sullivan has failed to cope with the pressure of the sport's key event after blowing a 10-5 lead against Selby when he looked certain to win a sixth world title six years ago – an outcome that would have left him one short of Stephen Hendry's record Crucible haul.
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The five-times champion has recently complained about the media demands of the game and concedes he does not enjoy the World Championship's elongated format with a top-16 seed needing to win 71 frames over 17 days in Sheffield to claim the title.
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The Essex player has twice reached the quarter-finals in 2015 and 2017, but has only won six matches at the venue in the past five years including a quite dreadful 10-8 defeat to amateur qualifier James Cahill in the first round a year ago when six-times winner Steve Davis accused him of taking liberties with the game.
Foulds feels O'Sullivan - champion in 2001, 2004, 2008, 2012 and 2013 - could have "one more in him," but is not overly confident that the 44-year-old is green baize icon is up to the challenge of coping with the Crucible.
"He can definitely win it, but the pressure seems to get him to these days," said Foulds on Instagram.
"When he played James Cahill last year, he played some odd shots in that match in that opening session.
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"It is like he's not really relishing being back there.
"Winning it five times is not bad if you don't like it. When he lost that final to Selby in 2014, he's not been the same player since then.
"He's not been back to the one-table set-up (of the semi-finals and final)."
O'Sullivan has not won a ranking event in the UK since picking up the Tour Championship in March 2019 and has dropped out of the world's top 16 on the one-year list with his lack of commitment to tournament play catching up with him.
This year's delayed event is due to start on Friday July 31 and is likely to be played behind closed doors due to the global health crisis with the final concluding on Sunday 16 August.
"If the World Championship had happened in April, he had his best chance for three years because the pressure in a strange way was off him I felt," said former world number three Foulds.
"The fact that he had quite a bad season, he hadn't done much at all.
"I think he might have one more in him because I still think he is..if he is not the best player, he is still in the top three.
"Judd Trump, Neil Robertson, Mark Selby and one or two others, but he is up there."
Hendry feels it is astonishing O'Sullivan has endured such a baffling barren run.
"I find it astounding someone as good as him has not won it for seven years," said Hendry. "He obviously doesn't like the long slog of it."
O'Sullivan's five-year Crucible record
- 2019 Lost 10-8 James Cahill (first round)
- 2018 Lost 13-9 Ali Carter (second round)
- 2017 Lost 13-10 Ding Junhui (quarter-finals)
- 2016 Lost 13-12 Barry Hawkins (second round)
- 2015 Lost 13-9 Stuart Bingham (quarter-finals)
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