Ramsey opens scoring for Gunners, Torreira shot deflects in off Koulibaly
Alonso heads in for Chelsea with five mins to go in Prague
Hazard & Kante come off bench for Blues in second half
Benfica beat Eintracht Frankfurt & Valencia win at Villarreal in other ties
Anthony Taylor at Benfica v Eintracht Frankfurt:
1 red card, 1 penalty awarded, 2 yellow cards.
Michael Oliver at Villarreal v Valencia:
2 penalties awarded, 2 yellows.
Busy...
Image source, EPASlavia Prague 0-0 Chelsea
Ross Barkley attempts a 'Cruyff' in the Slavia area and goes down in the area in between two defenders.
Half hearted appeals are met with a half hearted response from referee Felix Zwayer.
Arsenal 2-0 Napoli
Elseid Hysaj (Hi Elseid!) picks up a yellow for bringing down Alexandre Lacazette with a fairly crude challenge.
Image source, ReutersArsenal 2-0 Napoli
About time lads. We are finally under way in north London.
Slavia Prague 0-0 Chelsea
We are under way at the Eden Arena.
The Napoli players are waiting for the home side to come out of the tunnel at the Emirates...
Arsenal 2-0 Napoli
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What a game in Lisbon!
After the 10 men of Eintracht Frankfurt draw level against Benfica through Luka Jovic - who is on loan from Benfica - the Portuguese leaders regain the lead through Joao Felix's second goal of the night.
It's 2-1 to Benfica at the break.
Image source, EPAArsenal 2-0 Napoli
Lorenzo Insigne really should have scored - the Italian is teed up by Jose Callejon's pullback but fires his shot high over the bar. It did take a unwelcome bobble, admittedly.
At the other end Aaron Ramsey's shot is dealt with Alex Meret.
Unai Emery, unlike Sarri, will be very content.
Image source, ReutersSlavia Prague 0-0 Chelsea
Chelsea have had plenty of possession but, aside from Willian's strike which hit the bar, have barely troubled keeper Ondrej Kolar.
And that is that for the half - surely Maurizio Sarri will not be content that display?
Image source, Getty ImagesArsenal 2-0 Napoli
Pierre-Emerick Aubameyang is at it again.
This time he is slipped in on the right by Ainsley Maitland-Niles but his attempt to dink it over Alex Meret fails.
Maybe if he had one of Rory McIlroy's clubs.
Image source, PAMichael Oliver has awarded another penalty at Villarreal - this time to the home side.
There's a definite tug of Vicente Iborra's shirt by Valencia's Ezequiel Garay.
Up steps Santi Cazorla - and it's a belter by the former Arsenal man.
It's 1-1.
That's three penalties given by two English refs tonight - two by Oliver in Spain and one by Anthony Taylor at Benfica.
Image source, ReutersArsenal 2-0 Napoli
Alex Meret just about scrambles over to his right in time to block Pierre-Emerick Aubameyang's low trundler of a strike.
The keeper then collects the loose ball in time to prevent Alexandre Lacazette from slotting in the rebound.
A third is coming isn't it?
Image source, ReutersArsenal 2-0 Napoli
Another free-kick to Arsenal in a dangerous area.
Mesut Ozil's delivery eventually finds Aaron Ramsey, whose strike on target is blocked before Nacho Monreal concedes a free-kick in the opposition area after careering into a Napoli player.
Image source, ReutersThere's someone in the crowd at Villarreal with a trumpet blasting out Frankie Valli's 'Can't Take My Eyes Off You'.
Superb.
Valencia lead 1-0 in the all-La Liga quarter-final.
Image source, EPAArsenal 2-0 Napoli
Alexandre Lacazette has his head in his hands milliseconds after pretty much air-kicking Pierre-Emerick Aubameyang's square ball to him just inside the area.
One to forget for the Frenchman - he'll probably score with his next chance though!
Image source, Getty Images#bbcfootball
Anteneh Ademe: Arsenal are almost guaranteed to concede so i think we will need 3 or 4 goal to have any serious advantage in this first leg.
Positive thinking Anteneh!
Image source, Getty ImagesEnglish referees are very much in the spotlight tonight.
After Michael Oliver awarded Valencia an early penalty at Villarreal, Anthony Taylor is taking charge of Benfica against Eintracht Frankfurt - where the hosts have taken the lead through a spot kick.
Taylor has also dished out a red card to Frankfurt's Evan N'Dicka.
Slavia Prague 0-0 Chelsea
The Blues come within an inch of scoring as 's crackerjack of an effort from 20 yards comes off the bar.
A truly stunning strike.
Image source, Getty ImagesPortuguese leaders Benfica are ahead against Germany's Eintracht Frankfurt.
It's come from the penalty spot - Joao Felix scoring after Gedson Fernandes is fouled.
Frankfurt are also down to 10 men after French defender Evan N'Dicka is shown a straight red after his foul on Fernandes.
Image source, Getty Images
Lucas Torreira
Lucas Torreira does exceptionally well to dispossess Fabian Ruiz about 25 yards from goal. He then leaves Ruiz baffled with a trick before firing a shot that takes a heavy deflection off Kalidou Koulibaly, who was attempting to make a hat-trick of blocks in the match.
They've decided to give the goal to Torreira.
What a start for the Gunners - unexpected?
Image source, Reuters
Image source, Reuters