Mark Selby beat Xu Si of China 4-2 in the first round of the Northern Ireland Open at the Waterfront Hall on Monday.
Selby won the first frame with a break of 78 but his opponent took the next two, before missing a simple black which would have taken him two clear.
A 64 break edged Selby 3-2 ahead and the world number six also won the next.
As the winner of the English Open, Selby is the only player who can lift a £1m bonus for winning all four tournaments in the Home Nations Series.
The three-time world champion beat David Gilbert 9-1 in the final of the English Open in Crawley last month, with the Scottish Open to come in December and the Welsh Open in February.
Among the other winners on the opening day in Belfast were former World Championship finalist Ali Carter, who beat Robert Milkins 4-1, and 2017's beaten NI Open finalist Yan Bingtao, a 4-2 victor over Andy Hicks.
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Marco Fu defeated Gerard Greene 4-1, with Matthew Stevens seeing off Chris Wakelin by the same scoreline and the NI Open winner of two years ago, Mark King, crashing out 4-2 to Thailand's Thepchaiya Un-Nooh
Former world champion Ken Doherty progressed 4-2 at the expense of Michael Georgiou and Stephen Maguire eased past Northern Ireland amateur wildcard Declan Lavery 4-0.
The other two national wildcard competitors, Dungannon's Patrick Wallace and Antrim 15-year-old Robbie McGuigan, the stepson of Mark Allen, met in a preliminary round match with Wallace coming out on top in a 4-0 win.
Northern Ireland professional Jordan Brown overcame Thai player James Wattana 4-2 in the evening session.
World number five John Higgins beat Chang Bingyu by the same scoreline while Ding Junhui was one of the surprise first round exits, falling to a 4-2 defeat against David Lilley.
Former world champion Shaun Murphy swept past Fraser Patrick with a 4-0 win.
Defending champion and world number one Judd Trump, Antrim's Mark Allen, newly crowned Champion of Champions winner Neil Robertson and crowd favourite Ronnie O'Sullivan all enter the round one fray on Tuesday.
The winner of the tournament collects £70,000 and The Alex Higgins Trophy.