Adam Williams
BBC Sport at Madejski Stadium

Most definitely not going to script this one so far.

Sheffield United, as expected, have had the majority of the ball but have done relatively little with it to open Reading up.

The hosts are scrapping their way through this tie as much as they can, but you feel they need another goal sooner rather than later to pull off a shock in normal time with the options Chris Wilder has at his disposal on the Sheffield United bench.

Reading want another penalty for a push at the far post but there's nothing doing this time...

Phil McNulty
BBC Sport chief football writer at Stamford Bridge

Jurgen Klopp's changes, with the introduction of Roberto Firmino and James Milner, were probably under consideration before Chelsea's second goal but it is a real uphill task now.

As for the goalscorer Ross Barkley, he is a real enigma. So much talent but often makes bad decisions - then shows you what he has got with a goal like that.

Dan: The aura of invincibility that Liverpool have given off for so long seems to be crumbling.

Eoghain: Was the club World Cup worth it? Liverpool's legs are showing the strain now.

Liverpool yet to have a shot on target in the second half as Joe Gomez shanks a long-ranger well wide.

Want to know how much Miguel Almiron loves the FA Cup?

Four of his six goals this season have come in the competition while the Paraguay forward was also heavily involved in his side's third goal at The Hawthorns.

Will he finish this tie with a hat-trick?

Liverpool send on Roberto Firmino and James Milner for Divock Origi and Curtis Jones.

Liverpool have 20 minutes to save this one.

Here's how Reading levelled it up - we're going to extra time as it stands. Nobody wants that.

Jermaine Jenas
Ex-Tottenham and Newcastle midfielder on BBC One

I have criticised Ross Barkley on a few occasions for taking the wrong option and I thought he had done the same here. I was thinking 'Play it to Pedro', but he took the responsibility and what a strike, he smashes it past Adrian.

He enjoyed that and he needed that.

Got to finish that?!

Liverpool are ragged again as they lose the ball 30 yards from the Chelsea area and Pedro can run it in from 70 yards! He runs out of legs a bit, can feel Joe Gomez and co closing in and in the end his shot from 20 yards is tame and easily saved.

West Brom almost get a goal back but Matt Phillips' attempt is hacked off the line by Danny Rose after the West Brom man lobs Karl Darlow.

Alistair Magowan
BBC Sport at The Hawthorns

Valentino Lazaro gets his first goal since a loan move from Inter Milan in January but it was made by Miggy Almiron, whose lovely pass picked out Allan Saint-Maximin in the build-up.

Not sure I can see West Brom coming back from this. Newcastle are on course to reach their first FA Cup quarter-final of the Mike Ashley era.

Keith Edwards
Ex-Sheffield United striker on BBC Radio Sheffield

The home team will get forward in this second half. They’re playing with the freedom to do so.

It’s a nice open game of football, with both teams going for it. That’s what we want to see in the FA Cup.

Don Hutchison
Ex-Liverpool midfielder on BBC Radio 5 Live

That is a sensational finish from Ross Barkley.

He was in the middle of the park, the defenders were backing off and it completely opened up for him.

He drove on from his own half, he could have passed it to Pedro but smashes it into the bottom corner.

Jermaine Jenas
Ex-Tottenham and Newcastle midfielder on BBC One

Beautifully struck. When he hit that, Mason Mount's eyes would have lit up. He doesn't give it enough time to come down, but what a strike. Adrian was not getting to that.

Chelsea have a free-kick in a good area, they have three men over it. Mason Mount addresses the ball and pings it nicely - off the top of the bar!