A late rally from Ronnie O'Sullivan was not enough as Ricky Walden won a deciding frame to advance to the quarter-finals of the Welsh Open.
O'Sullivan hit breaks of 88 and 85 to rally from 3-1 down and force a deciding frame, but Walden got back in gear in the seventh.
He won an early battle of the safeties and then made a break of 83 before shaking hands.
It was the second time in the day O'Sullivan had needed to dig deep, having twice come from behind to beat Ding Junhui 4-2 earlier in the day to reach the last 16.
Judd Trump advanced with a 4-1 win over Jimmy Robertson as he began to rediscover some form, taking the final frame with a break of 100.
Ali Carter beat Scott Donaldson 4-2, Zhang Ada saw off Matthew Stevens 4-2, and Hossein Vafaei edged out Ryan Day 4-3