Reigning champion Jack Lisowski began his defence of the Northern Ireland Open with a 4-1 victory over Huang Jiahao in Belfast, but Mark Selby made a surprise first-round exit.
Lisowski, 35, won his first ranking title at the tournament last year and raced into a three-frame lead over his Chinese opponent at the Waterfront Hall.
The Englishman allowed Jiahao to cut the deficit to 3-1 but would clinch the fifth frame on the black to advance.
He will now face Scotland's Anthony McGill, who enjoyed a 4-1 victory of his own over Stephen Maguire, in round two.
While Lisowski ensured safe passage into the second round, there were surprises on the opening day of the tournament with Selby and Xiao Guodong both beaten in round one.
Four-time world champion Selby was hoping to become the first player to win the quartet of Home Nations tournaments, but was beaten 4-2 by Louis Heathcote.
The world number five, who has already won the China Open this year, led 2-0 but dropped four straight frames to exit.
Xiao Guodong, meanwhile, lost a final-frame decider to England's Sam Craigie and Cork's Aaron Hill was also beaten in the first round with a 4-2 defeat by Thailand's Thepchaiya Un-Nooh.
Former world champions Neil Robertson and Shaun Murphy are among those in action during Sunday's evening session beginning at 19.00 BST.