O'Sullivan is aiming to win his third successive ranking event
World champion Ronnie O'Sullivan saw off Stuart Pettman in the first round of the Shanghai Masters - but defending champion Dominic Dale is out.
O'Sullivan was matched by Pettman, the world number 62, in the early stages and was level at 2-2 before breaks of 73, 60 and 86 gave him a nervy 5-2 win.
Dale, the world number 32, was pipped 5-4 by Steve Davis.
And fellow veteran Jimmy White's good run of form was ended by Mark King, who triumphed 5-4.
O'Sullivan is aiming to clinch his third successive ranking event title but was given a tougher than expected test by Pettman, who came through Monday's wildcard round.
"I felt nervous to begin with because I want to do well in this tournament," O'Sullivan said.
"The people in China have been good to me so I owe them something. I felt under pressure to win. Maybe I need to relax and enjoy it more."
Dale, the world number 32, went 2-0 up against Davis but soon found himself 4-2 down before forcing a decider.
It was Davis who came out on top, thanks to a break of 54 in the ninth frame, and he will play either Ding Junhui or Dave Harold in the last 16 on Thursday.
Elsewhere, world number four Mark Selby claimed a stunning win over 19-year-old Judd Trump 5-1 thanks to breaks of 88, 105, 85, 75 and 75.
Selby said: "I didn't miss a ball and had a 70-plus break in every frame. It's the first time I've played Judd so I didn't really know what to expect other than he's a dangerous player.
"I reached the semi-finals here last year and would like to go one better. I enjoy coming to China in general and really enjoy the support here."
But seven-time world champion Stephen Hendry lost at the first hurdle, going down 5-4 to Flintshire's Ricky Walden.
"There's no excuse, I just didn't play well enough to win. It's as simple as that," Hendry explained. "I just have to keep working hard and hope the results come."
Australia's Neil Robertson beat Ireland's Fergal O'Brien 5-2, world number five John Higgins beat Tom Ford 5-4 and Joe Perry beat Matthew Stevens 5-1.