World Snooker Championship: O'Sullivan conqueror James Cahill suffers shock exit to teenager Mertens

Cahill is ranked a lowly 106 in the world despite his 10-8 win over five-times champion O'Sullivan in the World Championship first round in April 2019 – arguably the biggest upset in the modern history of the event – and his poor run of form this season continued as Belgium's Mertens subjected the giant slayer to a taste of his own medicine.

In claiming a notable victory in the first round qualifier, he is the youngest player to win a match at the sport's blue-chip tournament.

The World Open Under-16 champion Mertens is a raw but fearless potter and grew in confidence the longer the match progressed at the Sheffield Institute of Sport with Cahill toiling for consistency.

24-year-old Cahill started the evening positively with a run of 82, but the warning signs were there as a 55 was cancelled out by a 63 from his teenage opponent in restoring parity at 1-1.

The next three frames fell to Mertens as Cahill struggled to escape from his state of torpor with the former Belgian Under-18 champion rolling in a 57 in the fourth frame.

He had the chance to reduce the deficit to 4-2 after Mertens had broken down on 48, but a missed brown proved crucial as Mertens potted brown and blue to move to the cusp of victory and a meeting with Sam Baird in the second round.

Cahill ran in a lovely 90 in the seventh frame to keep alive his hopes, but Mertens opened the eighth frame with a knock of 48 to apply some more heat. Cahill was unlucky when he saw a white fly into a pocket after potting a long red and it proved to be the end of his hopes despite playing on for snookers.

There was no similar fairytale for 14-year-old Ukrainian Iulian Boiko, was lost 6-3 to Malaysian Thor Chuan Leong earlier in the day.

Thor made breaks of 68, 63, 68, 83 and 69 to progress to a meeting in the second qualifying round with Ian Burns.