Ronnie O'Sullivan's title defence at the World Grand Prix lasted just six frames as he was beaten 4-2 by Marco Fu.
O'Sullivan cruised to the title 12 months ago at Preston's Guild Hall, but was well below his best at The Centaur in Cheltenham as Fu progressed to face Barry Hawkins, a 4-1 winner against Ryan Day.
Fu hadn't beaten O'Sullivan in a decade, his last success coming in the 2009 Welsh Open, and the early signs weren't encouraging as breaks of 68 and 51 earned The Rocket the opening frame.
Fu took the next two frames before a break of 77 from O'Sullivan levelled the scores, and then came the pivotal moment in the match as O'Sullivan missed a simple yellow when appearing certain to edge the fifth frame.
O'Sullivan had been handed a gilt-edged opportunity after Fu had missed when in the balls, but having done the hard work missed yellow off the spot to effectively surrender the frame.
Fu capitalised by knocking in an excellent long red at the start of the next and when O'Sullivan recklessly attempted a long red when trailing by 47 points, Fu was presented with a ticket to round two.
In winning, he became just the third player this season - after Mark Davis and Judd Trump - to defeat O'Sullivan.
On the other table, Hawkins laid down a marker of his own with breaks of 130 and 143 to beat Day.
The Welshman had in fact started the match with a quality 127 break of his own, but Hawkins was unstoppable thereafter and signed off with a sumptuous 143 to cruise into the second round, where he'll meet Fu.
In the same quarter, former world champion Stuart Bingham beat Zhao Xintong 4-1.
Bingham started the match with breaks of 131 and 102 to cruise into the second round, where he could meet German Masters winner Kyren Wilson.
Finally, Mark Allen held off a fightback from Gary Wilson to advance to the second round with a 4-2 win.
Monday's results
- Marco Fu 4-2 Ronnie O'Sullivan
- Barry Hawkins 4-1 Ryan Day
- Stuart Bingham 4-1 Zhao Xintong
- Mark Allen 4-2 Gary Wilson
