Ronnie O'Sullivan has been a little bit stop-start so far. After a shaky opening frame Si Jiahui has settled now and is playing with a lot more finesse.

Si pots the blue in the middle pocket in the third frame to break open the pack of reds, but after break of 30 takes his eye off the cue ball and misses a pretty easy red.

Can the Rocket make him pay?

Shaun Murphy
2005 world champion on BBC Two

That was a shot across the bows of HMS O'Sullivan from Si Jiahui which says I'm here, I'm not going to panic. He just has to do that 12 more times and he'll be in the semi-finals! That's how you combat the force that is Ronnie O'Sullivan - when you get your chance hit him hard and see where it takes you.

This frame will have done Si Jiahui's confidence the world of good.

He's dispatched all the reds and then pots the green for a century break. He's not able to complete the clearance after rattling the brown against the jaws of the pocket but signs of form on the baize regardless.

All square.

Stephen Hendry
Seven-time world champion on BBC Two

Si Jiahui is under not as much pressure because nobody expects him to win. But in terms of the overall picture he just needs to try to play his own game and see where it gets him.

An equally scrappy start to the second frame before Si Jiahui starts to find a little bit of form with the cue. He's got a break of 55 out of 60 points, with 75 left on the table.

Ken Doherty
1997 world champion on BBC iPlayer

He really is an entertainer, Luca Brecel. He plays with such panache. A wonderful break.

Anything you can do, I can do better.

Luca Brecel smashes in a long red and scatters the others.

He's soon up to 92 and levels the frame scores with Judd Trump.

Shaun Murphy
2005 world champion on BBC Two

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 seems strange to say that but we know that 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.

Si Jiahui is unable to get his act together and Ronnie O'Sullivan sets about working the colours. He's sufficiently ahead by the time he fouls on the blue for Si to concede the frame.

A bit of a messy start to this one, overall, though.

Stephen Hendry
Seven-time world champion on BBC Two

This has been a very scrappy start by both players. Si Jiahui has not settled at all - he looks like a rabbit in headlights at the moment. The only positive is his opponent does not look at the races either.

A tut and a shake of the head from Ronnie O'Sullivan as he rises from the table having blundered on a straightforward red to allow Si Jiahui another visit. That frame was probably there for the taking for the Rocket. He might have to battle it out from here.

John Parrott
1991 world champion on BBC iPlayer

What an onimous start this is. Luca knows what he's up against.

Hold on to your hats. We're off to a quickfire start already on table two.

World number one Judd Trump in full flow.

He quickly racks up 71 to take the first frame.

Luca Brecel tried for the two snookers he needed to have a chance of levelling but Trump was up to the challenge.

Image source, PA Media

Steve Sutcliffe
BBC Sport at the Crucible Theatre

Image source, BBC Sport

What an afternoon.

Tudor Square is packed with snooker enthusiasts grabbing a drink and settling in for the long haul in front of the giant screens and the Crucible is still bubbling to see how Ronnie O'Sullivan fares here as he continues his bid for a record eighth world title in the modern era.

But with the sun shining, the autograph and selfie hunters have also been out.

A little earlier crowds of people were keen to grab photos and get autographs from Zhao Xintong after he went 6-2 up against Chris Wakelin.

The 28-year-old could of course potentially meet 'The Rocket' in the semi-finals.

Si Jiahui is unable to capitalise and misses a relatively routine black into the corner pocket. The black is now stranded up the table behind the yellow but Ronnie O'Sullivan sets to work on the pink with the pack of reds.

Image source, BBC Sport

An early break of 20 from Ronnie O'Sullivan but, using the rest, he rattles a red into the jaws of the corner pocket at the top of the table to give Si Jiahui an early opportunity.

This is the third meeting between these players. One apiece so far.

Stephen Hendry
Seven-time world champion on BBC Two

Ronnie O'Sullivan is not at this brilliant best, obviously, but he still has that aura and intimidation factor. The two players he's played so far have crumbled in the face of that. That's almost as much as playing well. If he brings better form with his long game, because his scoring his always there, he can be a major contender.

So, we'll have live coverage of Ronnie O'Sullivan v Si Jiahui on BBC Two while the other quarter-final between Judd Trump and Luca Brecel will be available to watch via BBC iPlayer.

You can, of course, watch both matches by clicking the 'Watch & listen' tab above.

Dennis Taylor
1985 world champion on BBC Two

To be honest I never take a lot of notice of what Ronnie says about how he's playing because it's often not a reflection of how he is out on the table. He's only lost eight frames so is in pretty good form. The new cue is giving him a few issues but only on long shots when he has to play with a bit of side. His break building is as good as it has been.