An immediate response from Ernesto Valverde on the Barca bench.

Aleix Vidal is on in place of Paulinho.

Jack Tanner: Will.i.can

Nikhil: Willlyyyyyy ... Third time’s a charm.

Sir Fabian Pavez: If Chelsea wins this tie over two legs, I reckon they'll win this seasons UCL.. Classic goal from a Classic Brazilian.

Image source, Reuters

NORTH: I practically don't think we need Pedro in this game, a Giroud would be more rampaging allowing Hazard and willian more free space.

Michael Reid: Surely I'm not the only one who hasn't been impressed with Barcelona tonight. I can't help but think if they got drawn against City this tie would have been over by now...

Thibaut Courtois comes and gathers again from a Barcelona corner.

He is the commander-in-chief of that penalty area.

A delicious piece of skill from Luis Suarez, chopping the ball back against the grain to leave Andreas Christensen in the queue for a a hot-dog.

Victor Moses has his team-mate's back though and slides in to make the tackle and concede the corner.

Which Thibaut Courtois comes and claims with space to spare.

Eden Hazard has been word perfect so far, but he forgot his lines there. The Chelsea man stumbles and the ball escapes his control as he gets the chance to run at the Barcelona defence.

Sir Fabian Pavez: If this ends 0-0 at the bridge, Chelsea will have an upper hand at the Camp Nou.

Barcelona are probing, keeping the ball and swapping angles in search of a weakspot in the Chelsea rearguard.

They almost find it.

Luis Suarez - quiet so far - darts onto a ball in behind and digs out a decent low effort from a tightening angle, but Thibaut Courtois' big left hand is down to divert it wide of the post.

Eden Hazard slumps to the floor as he receives the ball with his back to goal and Samuel Umtiti in close attention in the box.

That looked six of one, half a dozen of the other. Hazard was backing into Umtiti as much as Umtiti with pulling at his shoulder.

Nothing doing from the referee.

Barcelona are back on the ball and in control, trying to take some of the momentum out of a Chelsea side who had build up a head of steam by half-time.

Andres Iniesta attempts to roll back the years to 2009 semi-final as the ball pops up to him 20 yards out, but this time the ball lands in the stands rather than the top corner.

Image source, EPA

Samuel Maiwada: It's shocking how people still rate ball possession over chances. All the times Chelsea beat Barca in the CL, the latter had possession. Tactics!

Maybe that is why they don't sling it into the mixer more often.

Sergi Roberto squanders a great position out on the right wing with a horribly over-hit cross for Barcelona.

No changes by either side at the break.

Might Antonio Conte be tempted to throw Olivier Giroud or Alvaro Morata into the mix if it remains the same into the final quarter?

Barca get us going...

Abhie Speaks: With a 2nd leg still to come and Barcelona being the opponent Chelsea can't get away from the fact that a 4-0 victory too can't guarantee qualification ... *Cough* #PSG .

Eidur Gudjohnsen - a man with a foot in both camps - is at Stamford Bridge to watch this one.

Andy Townsend
Ex-Republic of Ireland international on BBC Radio 5 live

It is a different Barcelona to the one we saw when Luis Suarez, Neymar and Lionel Messi were united in attack.

In the past few years, when they’ve started to play against some of the very big teams away from home in the first leg, they’ve left themselves too much to do.

I think they’re mindful and aware of Chelsea’s capabilities up front.

AndyK: Chelsea need to bring Will Grigg on in the second half!

Simon Goodall: Willian just needs to hit the bar now for the perfect "nearly hat-trick".