Mark Williams, the three-time world champion, blamed Covid after falling asleep in his chair during a surprise defeat in the UK Championship second round.
Williams, the world No 8, could be seen battling to keep his eyes open on multiple occasions during his 6-5 loss against 56th seed Anthony Williams.
The Welshman missed two tournaments last month after contracting Covid and later apologised for falling asleep in the sixth frame of Sunday night’s match.
“Thirty years as a professional, that’s the first time I’ve ever fell asleep in the chair,” said Williams.
“It was 3-2 and I was out. My head went down, and I woke up and I didn’t have a clue where I was for about five seconds. It was a bit embarrassing but I was just shattered.
“I need to be playing in the mornings really, or afternoons. The more the day goes on the more tired I get.
“It’s disappointing but there’s a lot worse people that have had Covid than I’ve had it, so I’m one of the lucky ones really.
“It’s definitely better than what it was a couple of weeks ago so I’ve just got to keep going, but if I play night matches I’m going to really struggle.”
Williams had eased into a 3-0 lead in the match before Hamilton fought back to win the next two frames. Williams then struggled for momentum as he battled to stay awake, with Hamilton benefiting from a fluke on a red during a match-winning break of 70 in the deciding frame.
“I’ve had enough flukes in my time, so you’ve got to take one the other way now and again,” said Williams.
Next in action at the Scottish Open on December 6, Williams added: “It’s only best of seven [frames], so I should be able to stay awake for that one.”
Williams was joined late on Sunday by world No 1 Mark Selby in an ever-growing list of shock early losers at the York tournament. Selby lost 6-2 to Iran’s Hossein Vafaei after defeats to defending champion Neil Robertson, former winner Shaun Murphy, Masters champion Yan Bingtao and three-time winner Ding Junhui.
“I didn’t play good enough,” said Selby. “Hossein was definitely the better player and deserved to win. He started off great and is a great front-runner, and if you let him get away he can blow anyone away.”