LONDON - China's debutant Si Jiahui edged out Anthony McGill 13-12 to reach the semifinals at the Snooker World Championship in Sheffield on Wednesday.

Si, 20, grabbed his chance to play at the Crucible Theatre for the first time after winning three matches in the qualifiers. The world No. 80 then saw off 2005 champion Shaun Murphy and veteran Robert Milkins to set up a clash with McGill.

In a seesaw encounter, Si kept his cool to beat the 32-year-old McGill, who reached the quarterfinals at the World Championship for the third time in four years.

Si will face Luca Brecel in the semifinals as the Belgian came from 10-6 down to knock out seven-time champion Ronnie O'Sullivan 13-10.

"To win seven frames in a row against Ronnie is probably the best session I have played," said the 28-year-old Brecel, who reached the semifinals at the worlds for the first time. "I was so composed for the whole match, I felt very calm, even at the end."

Defending champion O'Sullivan hailed Brecel as an unparalleled talent. "I've never seen a talent like that before. No one plays like that, it's impossible."

Mark Selby ousted veteran John Higgins 13-7 to set up a semifinal clash with Mark Allen, as the nine-time ranking event winner defeated qualifier Jak Jones 13-10.