Every credit to the young man, he's performing in the biggest match of his life. He is playing his hero in the Crucible, it doesn't get any bigger than this.
O’Sullivan 12-9 Si
He's not been vintage for most of tonight but there's glimpses of greatness amongst the mediocrity, for sure. Si has potted another gangbuster long red to have the first chance of frame 22...
#bbcsnooker, via WhatsApp on 03301231826 or text 81111 (UK only, standard message rates apply)
Man, I have missed watching Ronnie O’Sullivan. What a player.
Otis
O’Sullivan 12-9 Si
A clearance of 35 and O'Sullivan has won it 65-54!
He's one frame from the last four!
Image source, PA MediaBlue, pink and black remain...
Ken Doherty
1997 world champion on BBC iPlayer
That's one of the shots of the championship! What a steal of a frame this would be.
O’Sullivan 11-9 Si
Woooww where has that come from?! Ronnie reaches deep into his arsenal for a fantastic long pot down the rail. He's in the balls and could clear up...
O’Sullivan 11-9 Si
Two reds left. Tight on the cushion. And O'Sullivan misses the first. It's 29-54 in the frame...
O’Sullivan 11-9 Si
John Virgo
1979 UK Championship winner on BBC Two
It's a chance. Not the best of chances.
But a chance.
O’Sullivan 11-9 Si
Ronnie O'Sullivan is taking no time at all over every shot, just almost racing through them. He's left another long pot on and Si is a mile away from it, before it hits the yellow and rattles the jaws!
Chance for O'Sullivan. A tough one.
Result: Trump 13-8 Brecel
Five consecutive frames tonight and Judd Trump seals his place in the semi-finals.
He'll be a hard man to beat but has a tough old opponent in Mark Williams in the last four. Their match begins on Thursday evening.
O’Sullivan 11-9 Si
A very tough red is missed to bring Ronnie back to the table. He trails 54-9.
O’Sullivan 11-9 Si
A fine green and a fantastic pink from Si Jiahui. He's being made to work for the tail end of this break though with reds on the cushion. The frame isn't won quite yet...
O'Sullivan 11-9 Si
Steve Sutcliffe
BBC Sport at the Crucible Theatre, Sheffield
A couple of years back Ronnie O'Sullivan also led Luca Brecel 10-6 going into the final session of a World Championship quarter-final.
Brecel then went on to win 13-10.
Is this Si Jiahui fightback going to result in another stunning result or will he be left to rue earlier missed opportunities?
The Crucible crowd are absolutely enthralled by which direction this contest is going to go in.
O’Sullivan 11-9 Si
Si Jiahui making moves. He's raced to 30-9 up with several reds still in the loose.
O’Sullivan 11-9 Si
I saw a video the other day of Mark Williams saying he barely practices any more, and Ronnie has hardly played all year. This is the WORLDS lads.
Si flukes a planted red and now has a chance of a decent break after a very good yellow off the rest.
O’Sullivan 11-9 Si
Scruffy stuff. Ronnie half flukes a red into the corner, cannons the blue and is left with an outrageous long brown that he makes but then runs too far and misses the red.
A bag of nails of a night for the great one. Hanging on in there.
O’Sullivan 11-9 Si
High stakes, long distance safety shootout stuff. Neither man can afford a costly error.
Ken Doherty
1997 world champion on BBC iPlayer
Every time Ronnie has to play a shot with side he is struggling. When he's in close he's ok but he's really struggling from distance.
O’Sullivan 11-9 Si
There's a lengthy break as the referee has to put the balls back after that foul and a miss from Si scattered them hither and thither. You can tick 'two-cushion escape' off your Crucible bingo card as Si lets Ronnie into the balls - but his cut is a figurative mile off.
Never got near the pocket.