Theo Walcott
Former Arsenal and Southampton forward on BBC Radio 5 Live

Image source, Getty Images

Everyone in the stadium feels like Arsenal can unlock this game.

It feels like Arsenal have gone away from their patterns of play, the way they have played the whole season. Porto have set that trap.

Mikel Arteta is talking to his players now and he will be telling them to get back to their own game. Porto have gone in with little fouls and stoppages, but he will be telling his players 'That's not us'.

It will be an interesting next 30 minutes.

These Champions League quarter-finals are looking really tasty.

Five teams guaranteed to be in the last eight so far and they're all big hitters.

• Barcelona (Spain)
• Bayern Munich (Germany)
• Manchester City (England)
• Paris St-Germain (France)
• Real Madrid (Spain)

Arsenal and Porto have extra time to come, with the final two last-16 second-leg ties coming tomorrow.

• Atletico Madrid (Spain) v Inter Milan (Italy) (0-1 after first leg)
• Borussia Dortmund (Germany) v PSV Eindhoven (Netherlands) (1-1 after first leg)

This is only the second time Arsenal have been taken to extra time in a Champions League match.

It's the first time since the 2008-09 last 16 tie against Roma - in which they eventually progressed on penalties.

Matthew Upson
Former England defender on BBC Radio 5 Live

That is ridiculous from the linesman.

It is a clear offside, just get your flag up.

This is when we start to discuss injuries happening, tired legs and he has let the game run on far too long there.

No winner. We're heading to extra time.

My word, that was nervy.

Francisco Conceição was offside but the flag didn't go up until he pings a dangerous cross into the box and Arsenal frantically clear it.

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Barcelona are into the quarter-finals. Could Xavi win the competition in his final match in charge? His side are still in it but had to work really hard to see off reigning Italian champions Napoli.

A hugely entertaining watch, with Barcelona seeing the job through, with Robert Lewandowski's late goal easing the stress.

Alan Varela can't shake his cramp. He's having to go off on a stretcher because he can't stand.

Former Liverpool players Marko Grujić is on in his place.

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Matthew Upson
Former England defender on BBC Radio 5 Live

You just have to marvel at how Martin Odegaard operates in those tight areas.

He just pirouettes past two defenders and does a neat one two with Bukayo Saka.

He goes to ground because he loses his balance in the end I think, not a foul.

Martin Odegaard tries to spin in the box and goes down. There's appeals for a penalty but the referee doesn't give it. Bukayo Saka felt he should have had a free-kick before that too.

Headed away at the near post.

Bukayo Saka almost pulls it back for Kai Havertz... Corner to Arsenal.

Matthew Upson
Former England defender on BBC Radio 5 Live

A goal now and it's all over.

Both teams are fighting really hard to create those opportunities.

What a tight match it is.

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Mathias Olivera thumps a strike against the crossbar for Napoli. That would've set up a frantic finish, but it's not to be for the visitors.

Image source, EPA

Robert Lewandowski has scored 13 goals in his last 13 knockout stage games in the Champions League.

Alex Howell
BBC Sport at Emirates Stadium

Porto are really trying to take advantage of any time they're in the Arsenal half. They just sent up both centre backs for a throw-in as they try and take the lead.

Into the final minutes now. Some big challenges are flying in.

Porto's Evanilson is off. On comes Mehdi Taremi up front.

Both managers making big attacking changes. They are going for it. This is fascinating.

Image source, Reuters

Bukayo Saka's corner is straight into the keeper's arms. Porto break and Declan Rice sprints back to make a crucial sliding tackle.