Porto try to quicken things up and it is played wide right to Francisco Conceicao, son of boss Sergio, and he gets into the penalty area but Gunners left-back Jakub Kiwior does well to stand up and not dive in and Arsenal get enough bodies back to clear the threat.

Barcelona's Frenkie de Jong gets a caution after wiping out Napoli captain Giovanni di Lorenzo and then arguing his case a bit too much.

Neil Lennon
Former Celtic manager on BBC Radio 5 Live

Porto are almost playing like an away team, taking their time on the ball unless it is in their own final third, trying to slow the play down at every opportunity.

Galeno has started quite brightly, has given Ben White something to think about early on but other than that Arsenal have not really been troubled.

Image source, Getty Images

A first look at the goal for Barcelona's Robert Lewandowski, but he is closely marked and at a tight angle and can only squeeze a shot wide of target.

Image source, Getty Images

Declan Rice received a yellow card after 65 seconds. That's the fastest card for an Arsenal player from the first whistle of a Champions League game since Abou Diaby in September 2012 (after 21 seconds v Montpellier).

Some panic from David Raya in the Arsenal goal. He has to dash out and kick the ball off the pitch. Porto quickly take a throw-in with Raya desperately retreating back into position, but the hosts can't capitalise.

Neil Lennon
Former Celtic manager on BBC Radio 5 Live

Arsenal have started well, they even had a high press on Porto earlier and forced them to pass the ball out of play. They are in no real danger at the minute and have seen plenty of the ball early on.

Porto will have expected a strong start from Arsenal, they will be patient and will look to be dangerous on the counter.

Image source, Getty Images

Lamine Yamal is running the show for Barcelona so far. He gets a shot away and forces a decent save from Alex Meret in the home goal. The rebound falls to Ilkay Gundogan and he opts to cross, but can't find a team-mate and Napoli manage to clear.

Barcelona have been the better side so far though.

Image source, Getty Images

Neil Lennon
Former Celtic manager on BBC Radio 5 Live

Martin Odegaard has been in great form in recent weeks, looks back to his very best.

He is one of those players in the Arsenal side that can make them tick. He has so much energy and quality on the ball.

An early chance for 16-year-old Lamine Yamal for Barcelona. He collects the ball inside the penalty area after a pass from Ilkay Gundogan and Yamal gets the ball on to his left foot but the curled effort flies well over the bar.

Image source, Reuters

Gabriel Martinelli tries to flick the ball through into the left channel for Arsenal but the old veteran Pepe is there to cut it out.

Neil Lennon
Former Celtic manager on BBC Radio 5 Live

That early yellow card may take something away from Declan Rice's game.

It is a foul, and a yellow card the way the modern game is, hard to argue with that. He'll have to be careful for the rest of the game now.

Image source, Getty Images

Declan Rice has got himself a booking after only 73 seconds. He has dived in on Galeno close to the right touchline and the Gunners midfielder, who captained West Ham when they won the Europa Conference League last season, has to be very, very careful from now on.

Image source, Getty Images

And away we go in Portugal and Italy.

Image source, Getty Images

Image source, Reuters

Image source, Reuters

Mikel Arteta’s young Arsenal squad had very little Champions League experience heading into a group stage they dominated, winning four games and progressing as winners with a fixture to spare.

Now the knockout stages present another chance for both manager and team to prove they belong at this level.

“We don’t have the experience, that’s the reality – 95 per cent of these players haven’t played this competition, they haven’t played the last 16," said Arteta.

“I haven’t (managed at this stage). But they have so much energy and enthusiasm to play well and that’s our desire and how we’re going to play the game.

“It’s great. We have earned the right to be here. It’s been seven years since we’ve been at the top table for these kind of matches and 14 years since we were able to go to the next stage.

“That’s the challenge. We know what is ahead of us, but we are very excited to face it and to go for it with full belief, that’s for sure.”

An extra incentive for Arsenal to banish past ghosts is the prospect of going all the way to just their second Champions League final, with Wembley playing host to the showpiece event this year.

“It should be incredible to have that feeling to lift that cup, in London, the first of June. It is there,” added Arteta.

“It is in our minds. It is a dream, but there are a lot of things you have to earn the right to do before that and we have a big obstacle ahead of us. We are really looking forward to it.”

James Horncastle
European football writer on BBC Radio 5 Live

Image source, Getty Images

Walter Mazzarri took over the Napoli job from Rudy Garcia in November and took over a side that was playing in a system and formation that was not his own.

This is a coach that has played 3-5-2 system for what feels like 700 years and then suddenly took over a title winning team that was used to playing 4-3-3, which clearly didn't work out.

The side went from fourth to ninth, and the Champions League places are 9-10 points away from them as it stands.

Francesco Calzona has been brought in on an interim basis, relatively unknown coach, who has a big job ahead of him. He needs to get off to a good start against Barcelona tonight, try and get the team into the top four, and then make sure the job still appeals to people come the summer.

At the age of just 16 years and 223 days, Barcelona’s Lamine Yamal is the youngest ever player to appear in a knockout stage game in the Champions League.

The only two 16-year-olds to start a match in the knockout stages of the competition both have done so this season (Yamal and Paris St-Germain's Warren Zaire-Emery).

Theo Walcott
Former Arsenal forward on BBC Radio 5 Live

The main goal when I was playing was Champions League, the top four was always the main aim for Arsene Wenger. That was it. It was an obsession for the manager and the squad.

We had the opportunity to go and win the league the year that Leicester City did it in 2016, but the Champions League was so important. But if I'm brutally honest I don't think any of us really believed we could actually go and win it.

For example the tie against Bayern Munich where we conceded so many goals [lost 10-2 on aggregate], showed exactly how far away we were from that level of winning it.

It has been a long time since then for Arsenal to get back into the competition, but now you see the players they have signed, the squad they have, they are in with a good chance.