Ronnie O'Sullivan said that Blackpool snooker ace James Cahill "played brilliantly" to eliminate him from World Championships in Sheffield but added that he had "no energy" and felt "absolutely horrendous".
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The world number one did appear to be having trouble keeping his eyes open during his stunning 10-8 defeat by the outstanding amateur from Marton.
Speaking to the BBC after being knocked out in the first round for the first time since 2003, the five-time world champion said: "I'm all right but my limbs feel really heavy. I'm absolutely shattered, drained and struggling to stay awake.
"You have to come here feeling physically and mentally good. Mentally I was feeling up for it after a good season.
"I didn't expect to do well, but you want to do your best and if your are not 100 per cent physically it's going to be even harder.
" I tried to hang in there to get through this match and have a few days off before the next round (Cahill's second round clash with Stephen Maguire begins on Friday)."
Of Cahill's performance, O'Sullivan said: "You could say he has played brilliantly and fair play to him, or you could say I kind of left him some pretty easy chances and allowed him to gain some confidence. But credit to him for getting over the line."
BBC pundit Steve Davis, the six-time world champion, said of Cahill: "What a fantastic performance under significant pressure.
"To hold himself together and pot those balls, knowing what a big deal this would be, he must be absolutely delighted."