Ahead of his Crucible clash with seven-times world champion Hendry 18 years ago, O'Sullivan infamously said he would like to send his opponent "back to his sad little life in Scotland".
It is a moment the Essex player always regrets – he later apologised to Hendry – but believes his close friendship with former world featherweight champion boxer Prince Naseem Hamed did not help before getting inside the ropes with his fellow 36-times ranking winner.
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"I wonder – rightly – whether he’s been listening to a certain Sheffield boxer with a penchant for shooting his mouth off," said Hendry in his autobiography Me and the Table.
"In the last couple of seasons, my pal Prince Naseem has visibly switched his loyalties from me to Ronnie, and the latter has been spotted hanging out with Naz’s entourage. So it’s not surprising there’s a bit of fighting talk."
Who is the greatest snooker player of all-time? Stephen Hendry or Ronnie O'Sullivan.
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The pre-match barbs backfired on O'Sullivan as he lost 17-13 to a fired up Hendry in the semi-finals, who also admitted it is the only grudge match he ever played at the iconic Sheffield venue.
Hendry rolled in breaks of 125, 124, 122, 113, 100, 81, 73, 65, 63, 59, 58, 55 and 53 as he won five of the last six frames to progress to the final, punching the air in completing victory.
"That was terrible. I blamed myself for that," said O'Sullivan.
"It should never have happened. But I'm also blaming Naz for getting me so revved up. He said to me the day before the match: 'You should be more like this, or more like that.'
"It was okay for Naz because he was a boxer, but I'm a snooker player. You have to respect your opponent. In boxing, they like that sort of trash talk to sell tickets. It wasn't really me. I was easily led. When I said it, and when it came out, I was gutted.
It is something I will always regret for the rest of my life. Stephen was my hero, and still is. I never a meant a word of it. I've told Stephen that, and apologised to him. I have a lot of time for Stephen, and he accepted my apology. We're good mates now – we have a solid friendship.
"It was a big mistake on my part."
Watch LIVE coverage of the 2020 World Championship and World Championship qualifiers live on Eurosport and Eurosport Player
World Championship first round draw
- Judd Trump Eng (1) v Qualifier
- Yan Bingtao Chn (16) v Qualifier
- Stephen Maguire Sco (9) v Qualifier
- Kyren Wilson Eng (8) v Qualifier
- John Higgins Sco (5) v Qualifier
- David Gilbert Eng (12) v Qualifier
- Jack Lisowski Eng (13) v Qualifier
- Mark Allen NI (4) v Qualifier
- Mark Williams Wal (3) v Qualifier
- Stuart Bingham Eng (14) v Qualifier
- Ding Junhui Chn (11) v Qualifier
- Ronnie O’Sullivan Eng (6) v Qualifier
- Mark Selby Eng (7) v Qualifier
- Shaun Murphy Eng (10) v Qualifier
- Barry Hawkins Eng (15) v Qualifier
- Neil Robertson Aus (2) v Qualifier
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