Defending champion Kyren Wilson has suffered a shock first-round exit at the World Snooker Championship, losing 10-9 to Chinese debutant Lei Peifan.
The world number two was eliminated despite entering the tournament after a superb season in which he won four ranking titles.
Seven-time world champion Ronnie O'Sullivan believes Wilson's packed schedule may have contributed to his downfall at the Crucible.
Wilson had opened up a 6-3 lead after the afternoon session but watched in disbelief as Lei reeled off six straight frames in the evening session to move into a 9-6 lead.
Ronnie O'Sullivan spoke out on Kyren Wilson's early Crucible exit
TNT Sports/PA
Despite battling back to force a final-frame shootout, Wilson was eventually sent packing after a gutsy break of 66 by the 21-year-old in the deciding frame.
O'Sullivan told TNT Sports that Wilson's busy year on tour may have finally caught up with him in Sheffield.
"I just think he played in too many tournaments he didn't need to play in," said the seven-time world champion.
"I see him playing [in one tournament], then the next day he's at Leicester playing for 7 or 8 days. Really, you want to be chilling out and putting your cue down."
O'Sullivan emphasised that Wilson's performance wasn't bad, but his schedule was problematic.
"I always think come in a bit undercooked. Take a month off from playing," O'Sullivan continued.
"If you can just take a little week off here and there from February, you can come in a bit fresher and you need to be for this tournament."
The Rocket suggested that preparation for the World Championship should begin months in advance."To win this World Championship, you need to come in doing well, but at some point around February, you need to say 'it's all about the World Championship'."
Lei Peifan triumphed against the odds over Kyren Wilson in a pulsating 10-9 win
PA
Wilson was keen to take positives from the defeat that saw him become the 20th first-time Crucible champion to fail to defend his title.
"Obviously it's really hard to take," said Wilson. "I've got such a strong record at the Crucible and I was nowhere near my best but it still took a 10-9 to beat me."
"It's been a really long season and I've done so much. I've never been stretched so much in all my life."
O'Sullivan, meanwhile, gets his own tournament underway against bitter rival Ali Carter on Wednesday.
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Kyren Wilson was left disappointed by his performance
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A victory would set up a round two clash with either Zhang Anda or Pang Junxu.
If the 49-year-old claims the title this year, it would mark his record-breaking eighth world crown.
Lei Peifan now awaits the winner of the match between Jak Jones and Zhao Xintong in the second round.
