Richard Morris: Ref 18:56 - Aguero is already doing that. Against WBA he ran 2kms more than last season's average of 8!

Tom Pennington: Disagree with Ally. Messi barely moves a yard when Barca don't have the ball. Luckily for them that's not very often.

Arsenal

Ludogorets Razgrad lost 6-0 to Arsenal in the reverse leg and they make a couple of changes from that game, including replacing keeper Vladislav Stoyanov with Milan Borjan. Striker Claudiu Keșeru also starts as Virgil Misidjan makes way.

Ludogorets Razgrad XI: Borjan, Minev, Palomino, Moti, Natanael, Abel, Dyakov, Cafu, Marcelinho, Wanderson, Keseru.

Arsenal striker Olivier Giroud makes his first start of the season, while midfielder Aaron Ramsey makes his first start since picking up a hamstring injury in the club's first league game of the season on 14 August. They are two of five changes from Saturday's win over Sunderland as boss Arsene Wenger also brings in keeper David Ospina, right-back Carl Jenkinson and midfielder Granit Xhaka. Petr Cech, Alex Oxlade-Chamberlain, Alex Iwobi and Mohamed Elneny drop to the bench, while Hector Bellerin is out injured.

Arsenal XI: Ospina, Jenkinson, Mustafi, Koscielny, Gibbs, Coquelin, Xhaka, Ramsey, Ozil, Sanchez, Giroud.

Ally McCoist
Former Scotland striker on BBC Radio 5 live

I think the 4-0 result probably flattered Barcelona 13 days ago.

The red card that City had, the first goal when Fernandinho slipped – all these things can be taken into account. Up to that point I thought City were doing ok and they’ll certainly have a better chance at home tonight.

If I was defending against those three - Suarez, Neymar and Messi - I wouldn’t take a chance. I’d probably concentrate as much on my defensive duties as much as you ever would in any game. You’re playing against arguably the best forward line in world football so if you make one mistake… 

The one thing that City will have to do tonight is to defend as well as they possibly can against this forward line. That means taking no chances.

Chris Bevan
BBC Sport at Etihad Stadium

Image source, BBC Sport

What's it like to face your former manager - not just any old boss, but someone who was a talismanic figure in your recent success, and part of the ethos of your club. Do you wish him well, and do you think he will succeed in his new job?

The answer to both questions was 'yes' for all of the Barca fans I spoke to outside the Etihad Stadium.

Xavi [not that one], who is here with his father Luis told BBC Sport: "I liked City before but I like them even more now Guardiola is their manager.

"I think Manchester City will win the Premier League. They started good and I know he has had a few problems recently, but I think and hope they will improve with Pep - apart from tonight of course!

"It is difficult to predict a score because City need the victory while for us the group is comfortable. We want to win, but they have to win - so I am going for a 2-2 draw."

'Well disciplined' could well be the key of course. Don't forget that City have had a man sent off in four out of their five meetings with Barca. 

Viv: Barca are beatable. Man City need a well-disciplined team, offensive & defensive minded (latter of which they are lacking)!

I thought City played well in Barcelona for large parts too. That slip from Fernandinho and then the almighty double error from Claudio Bravo called it a night but for periods they were looking very good indeed...

Ally McCoist
Former Scotland striker on BBC Radio 5 live

Reading between the lines, I think the manager is wanting Sergio Aguero to work harder.

We saw his goals at the weekend - sensational. He's clearly one of the best in European football at the moment, but Guardiola wants him to work harder off the ball.

Look at the Barcelona boys - when they don't have the ball they work hard, they have a shape; they defend as a team and attack as a team.

In my opinion Guardiola has been having a wee gentle dig at Aguero, saying it is all well and good scoring your goals, but imagine what he could achieve if he worked as hard off the ball.

John Murray
BBC Radio 5 live commentator

Image source, Getty Images

Anytime you’re going to watch that Barcelona front three of Messi, Suarez and Neymar then it stands apart. You’ll probably never see the likes of it again so every time you go and watch them – that is an attraction in itself.

But doubly so because of what we saw 13 days ago at the Nou Camp and the way that the game went then. It was 4-0 but I think there was enough in that to give City encouragement.

At home it’ll be really interesting to see how Guardiola and City play it and whether they can continue on the front foot the way they did for spells in the first game.

Chris Bevan
BBC Sport at Etihad Stadium

Image source, BBC Sport

What do you do when an unidentified (no colours, just totally black including the windows) team coach rolls up outside a stadium. Get your phone out, of course... who knows who might get out.

It was actually carrying Manchester City's players who have just arrived, greeted by a forest of smart phones and the sound of Oasis classic 'Morning Glory' blasting out of the speakers outside the stadium.

If that song is a question about what the story will be for City tonight, then the home fans will obviously be hoping for a different answer to their last five meetings with Barcelona, especially the last one when they made a good start but let it Slide Away...

Manchester City winger Raheem Sterling talks to Match of the Day presenter Gary Lineker about how new manager Pep Guardiola has influenced his playing style.

Watch more from Raheem Sterling on the Premier League show on BBC Two from 23:15 GMT on Wednesday.

A sixth defeat in six games against Barcelona would not mean the end of the road for Manchester City tonight, and with games against Borussia Monchengladbach and Celtic still to come Pep Guardiola's side would still be favourites to progress.

But it wouldn't half help their cause getting a good result tonight.

A home defeat last time out could prove potentially very damaging for Celtic.

If Celtic lose again tonight, and Manchester City avoid defeat against Barcelona, the Scottish champions' elimination from the running for a last-16 spot will be confirmed.  

Manchester City have already had one Champions League game postponed this season and there was a brief scare earlier this evening when the Etihad was briefly evacuated.

However, there was nothing much to worry about...

Image source, Reuters

Arsenal

Arsenal make five changes from the weekend, as Aaron Ramsey and Olivier Giroud return to the starting XI.

Full team news to come. 

Quite a few teams across Europe can clinch their Champions League progress today. 

Atletico Madrid will be into the last 16 if they beat FC Rostov at home. Bayern Munich will also be through if they win at PSV, so long as Rostov haven't beaten Atletico. PSV are out of the Champions League if they lose that.

Paris St-Germain will be through so long as they beat FC Basel and Arsenal don't lose to Ludogorets. A draw would be enough for PSG if Arsenal win.

Napoli are through if they beat Besiktas and Benfica and Dynamo Kiev draw their game. Napoli's game kicked off at 17:45 GMT in Turkey and is currently 0-0. Dynamo will be out of the Champions League if they lose and either Besiktas or Napoli win that early game.

Phil McNulty
BBC Sport chief football writer at The Etihad

Barcelona have won twice at The Etihad in the Champions League in recent seasons - so how can Pep Guardiola succeed where Manuel Pellegrini failed?

Guardiola has already said City will treat it like a final and they will be lifted by Sergio Aguero's two goals in a magnificent performance at West Brom on Saturday, where they won 4-0.

Barcelona are without the injured Gerard Pique and Andres Iniesta - but it gets more difficult after that.

Just how do City control Lionel Messi, Neymar and Luis Suarez? It is the question that is likely to decide the destiny of this match.

Image source, Rex Features

What do we think then - can Manchester City beat Barcelona tonight?

Are Arsenal the Premier League's best bet for Champions League glory this season?

Can Celtic pick up a positive result on the road?

Whatever your midweek musings, let's be having them. Text us on 81111 or tweet us at #bbcfootball. 

Image source, Getty Images

Barcelona make two changes to the side who won 1-0 at home against Granada on Saturday.

Sergio Busquets comes in for the match winner Rafinha, while Andre Gomes replaces former Manchester City player Denis Suarez.

Lionel Messi, Luis Suarez and Neymar lead the line as expected. A draw will put Barca into the knockout stages for the 13th consecutive season.