World No 80 Si Jiahui advanced to the quarter-finals of the World Snooker Championship after completing a 13-7 win over Robert Milkins on Monday afternoon.
Crucible debutant Si, the lowest-ranked player left in the tournament, resumed 11-5 in front and moved one from victory by edging a scrappy opener.
Milkins then won two frames on the spin, the first of those with a break of 69 after Si had missed match ball.
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However, the Chinese took the next with a break of 105 to secure a last-eight encounter against either Anthony McGilll or Jack Lisowski, who conclude their second-round match in Sheffield on Monday evening.
Si, who knocked out 2005 world champion Shan Murphy in round one, told the BBC: "I'm so surprised to get to the quarter-finals. I've even surprised myself. I'm just playing as if I am trying to learn from the other players.
"I'm very honoured to be in this position. I just wanted to play, perform and enjoy this Crucible experience."
World Snooker Championship - Quarter-final draw
- Ronnie O'Sullivan vs Luca Brecel
- Mark Allen vs Jak Jones
- Anthony McGill/Jack Lisowski vs Si Jiahui
- John Higgins vs Gary Wilson/Mark Selby