Si Jiahui shook off a warning by the referee over his attire to beat Ding Junhui 4-2 in the opening round of the Gibraltar Open.
The referee had a “strong word” with Si over the dress code as he started the match without wearing a bow tie.
But the incident didn’t phase the world No 89, who returned after the first frame with a bow tie and reeled off breaks of 58, 63 and 99 to take charge of the contest.
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World No 9 Ding, whose only previous appearance at the tournament came in 2017 when he lost in the second round, won the fourth frame with a break of 68.
Ding cut the deficit to 3-2 and then looked as though he might claw back a lengthy sixth frame to level the match.
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However, Si potted an excellent long red into the corner to clinch victory.
Masters champion Yan Bingtao also lost in the opening round, going down 4-1 to Jamie Clarke.
Shaun Murphy came from 2-0 down to win 4-2 against Ashley Hugill while Joe Perry won by the same scoreline against Mark Davis.
David Gilbert hit two centuries to book his place in the second round.
Defending champion Judd Trump is in action later on Monday evening while seven-time world champion Stephen Hendry makes his comeback against Matthew Selt on Tuesday.
Ronnie O'Sullivan and John Higgins have both withdrawn after reaching the final of the Players' Championship.
GIBRALTAR OPEN RESULTS
- Jamie Clarke 4-0 Yan Bingtao
- Alexander Uursenbacher 4-1 Yuan Sijun
- Zhou Yuelong 4-0 Xu Si
- Xiao Guodong 4-2 Martin O'Donnell
- Liang Wenbo 4-1 Brian Ochoiski
- David Gilbert 4-1 Paul Davison
- Jimmy Robertson 4-2 James Cahill
- David Lilley 4-2 Duane Jones
- Si Jiahui 4-2 Ding Junhui
- Mitchell Mann 4-0 Lukas Kleckers
- Robert Milkins 4-3 Gary Wilson
- Ricky Walden 4-3 Mark Joyce
- Rory McLeod 1-4 Hossein Vafaei
- Joe Perry 4-2 Mark Davis
- Shaun Murphy 4-2 Ashley Hugill
- Andy Hicks 1-4 Allan Taylor
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