Four-time champion Ronnie O'Sullivan eased past Scotland's Marcus Campbell 10-4 Saturday as he got his world championship defence off to an impressive start after almost a year spent out of the sport.
O'Sullivan will next face either Ali Carter, the man he beat in last year's final, or newcomer Ben Woollaston.
"Do I fancy my chances of going on and doing really well? Probably not but stranger things have happened, we'll just have to wait and see," O'Sullivan said.
"It's like trying to get fit for the marathon the day before the marathon starts. You're not going to do it." O'Sullivan led 7-2 after the opening spell and returned in the evening session with breaks of 102 and 90 as he sealed his last-16 place.