O'Sullivan had built a 10-6 lead heading into the resumption of the session and was the favourite to book his place in the final four.

But 'The Rocket' squandered his cushion in uncharacteristic fashion, failing to win a single frame and losing seven in succession as Brecel continued his superb run at the tournament.

The extraordinary defeat has now ended the 47-year-old's bid to move clear of Stephen Hendry to become an eight-time world champion.

"I didn't put up any resistance but you've still got to pot the balls and he played unbelievable," O'Sullivan told the BBC afterwards. "I wasn't playing well enough to have any impact on the game.

"If it was a boxing match they would have stopped it very early on. I was just pinching frames and hanging on.

"There's only so much hanging on you can do at the Crucible. It catches up with you at some point, and someone will eventually put you away."

Brecel - the world number 10 - had never advanced past the first round at World Championship but will now face either Anthony McGill or Si Jiahui in the semi-finals.

The pair's quarter-final match is finely poised with the score currently knotted at 8-8 heading into the final session, which gets underway at 7pm local time.