Last bit to go.

Image source, PA Media

Eddie Nketiah and Oleksandr Zinchenko are on for Arsenal. Leandro Trossard and Jakub Kiwior are off.

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

Image source, Getty Images

We are talking about moments all the time and Eddie Nketiah has got his here.

He has been waiting for his chance and has the opportunity to take one here. As a substitute that is your job, same as Oleksandr Zinchenko he has learned and won alongside the best, and will bring the calm that has gotten away from the game in recent minutes.

In Lamine Yamal (16 years, 243 days) and Pau Cubarsí (17 years, 50 days), Barcelona were the first side in Champions League history to start two players aged 17 or below in a knockout game.

Image source, Reuters

That's half of the extra time played. A quick turnaround before the final 15 minutes.

It's nervy.

Alex Howell
BBC Sport at Emirates Stadium

Mikel Arteta is waving his arms to the crowd asking for more noise.

Image source, EPA

Alex Howell
BBC Sport at Emirates Stadium

Kai Havertz just gave the Porto manager Sergio Conceicao a push as a ball that was played high up to him went out of play. It led to a small tussle between players but the referee calms it down.

Kai Havertz kicks a ball away off the pitch as Porto boss Sérgio Conceição is about to catch it.

Havertz then pushes him away and the visitors take offence. The referee comes across to cool things down and Havertz eventually apologises.

Matthew Upson
Former England defender on BBC Radio 5 Live

Just a little bit sloppy from Jakub Kiwior in the left back position.

Porto were quick to get bodies forward, had three or four players in the attack.

Worked wide to Mehdi Taremi but he can't keep his finish on target and it flies wide.

Image source, Getty Images

Two changes for Porto. Gonçalo Borges is on for Francisco Conceição and Stephen Eustáquio replaces Nico González.

Jakub Kiwior fails to deal with a long ball and Mehdi Taremi eventually cuts inside and curls it wide.

Bukayo Saka can't get past two defenders on the right. Declan Rice wins it back but his pass through to Saka is too heavy.

It's Arsenal who are attacking at the moment. Martin Odegaard wins a free kick, then Gabriel Jesus runs at Pepe but can't beat him on the left.

Image source, Reuters

Barcelona have reached the quarter finals of the Champions League for the first time since 2019-20, with them also knocking Napoli out of the last 16 that season (also 4-2 on aggregate).

Meanwhile, Napoli have been eliminated at this phase of the Champions League in four of the five times they’ve reached this round, with the Italian side losing five of their six away games in the knockout stages overall.

Martin Odegaard curls a free-kick delivery in. It's almost pounced upon by Bukayo Saka but it's quickly hoofed away.

Arsenal fans are ramping up the noise to encourage their side at the start of this extra time.

Matthew Upson
Former England defender on BBC Radio 5 Live

Image source, Getty Images

The emotion of these types of games is so intense that sometimes the game plan goes out of the window.

It is about which team can stay bettter focused and make the better decisions.

A lot of these Arsenal players haven't been in this position in this competition very often and it will be good experience for them.

It will be very interesting to see how it turns out.

Worth noting, we've not had a penalty shootout in the Champions League since the 2016 final.

Eight years ago. Crazy. Will we get one tonight?

Image source, Getty Images

Here we go then, extra time. Another tense 30 minutes? Bring it on.

A place in the Champions League quarter-finals up for grabs.