LONDON: Chinese sensation Si Jiahui earned a 5-3 lead after the first session of his World Snooker Championship semi-final against Luca Brecel on Thursday.

Si lost the first frame of the last-four clash at Sheffield’s Crucible Theatre, but hit back with clearances of 125, 102 and 97 to punish Brecel’s mistakes.

Belgium’s Brecel, who beat seven-time world champion Ronnie O’Sullivan in the quarter-finals, scrapped his way back to 4-3 down before succumbing in a nail-biting conclusion to the afternoon’s final frame.

Si was not even on the professional tour three years ago and as a debutant he had to win three qualifying matches to reach the Crucible.

The 20-year-old booked his semi-final place with a last frame decider against Anthony McGill on Wednesday.

Currently the world number 80, Si is the lowest ranked player to reach the World Championship semi-finals, although Terry Griffiths won the title as an unranked qualifier in 1979.

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In the other semi-final, Mark Allen finished the opening session against Mark Selby on a roll after winning the final three frames to lead 5-3.

A 123 clearance gave Selby the ideal start but uncharacteristic errors in the safety battles in the next two frames allowed his Northern Irish opponent to take control with breaks of 63 and 66.