Snooker legend Stephen Hendry branded Si Jiahui's miss on the black as "unforgivable" during the first frame of his quarter-final with Ronnie O'Sullivan. The Chinese potter had an early chance to put his opponent on the back foot, having got in early and a black on the spot would have put him in command.

However, Si missed the pot and Hendry on commentary for the BBC fumed at such an avoidable error. He felt that a player of Si's quality, with an opportunity to lay down an early marker, would be gutted to miss that shot.

"It’s the quarter-final of the World Championship," Hendry seethed. "In this level, against this level of opponent, it’s unforgivable. Not missing easy balls is going to be the difference between winning and losing this match for Si Jiahui. But it’s the difference between having the chance to win the match."

The ball was left stranded at the opposite end of the table, behind the yellow, and O'Sullivan had plenty of work to do, but he was able to start building up another break.

It was an error-strewn frame from both players, with O'Sullivan soon after missing a simple red. The frame was there for the taking but Si got back up from his seat when he would have expected to remain seated until the second break-off.

But Si was unable to make the most of his reprieve, looking "almost like a deer in the headlights" according to Hendry, and O'Sullivan tidied up the table by taking enough colours before fouling.

Shaun Murphy, on punditry duties for the Beeb after his exit in the previous round to Judd Trump, echoed Hendry's comments: "A catalogue of errors from both players in that first frame. The issue for Si Jiahui in this match is that it doesn't matter what Ronnie O'Sullivan does.

"It may seem strange to say that, but we know that at some stage, Ronnie will burst into life and play that high standard. For me it's about what Si does, and he's already shown signs of frailty. You cannot show too much of that to the Rocket."

After beating Ali Carter and Pang Junxu with relative ease in the previous rounds, O'Sullivan admitted he had been slightly lucky to reach the quarter-finals and claimed he was still underperforming.

He rated himself a "two out of 10" through his opening matches and questioned if Si would be the player to capitalise on that. If the 2023 semi-finalist can recapture his form from two years ago, he will have a serious chance to replicate that Crucible run.