Shearer: Man. City Must Deal With Man. United's Aerial Power

Saturday's Manchester derby will not define the season for United or City but it is a chance for both teams, and their managers, to show why they are a force to be reckoned with.

It is already clear these two sides will be in the mix for the title and both will want to make a statement of intent.

What adds even more spice to the occasion is that Jose Mourinho and Pep Guardiola both go into their much-anticipated first meeting in English football with 100% records after winning their first three league games.

Things are going very well for them, and their new players, but this is obviously the biggest test they have faced at their new clubs so far.

All things considered, it is brilliant for the Premier League that this match is happening so early in the season.

While the outcome will not tell us everything about United or City, it will reveal a lot more about how they are truly shaping up.

I am really looking forward to it. I think it will be a ferocious battle and it is extremely tough to call, although I probably favour United slightly because City have striker Sergio Aguero suspended, which is a massive blow for them.

I don't think City or Aguero had much of an argument that he did not deserve a ban for his elbow on West Ham's Winston Reid before the international break.

It was the right decision in the end but my only concern - which was also the reason City appealed - is Aguero was able to be punished retrospectively because referee Andre Marriner did not see the incident at the time.

I do wonder, if the referee didn't see it, what on earth was he looking at?

Kelechi Iheanacho, Nolito or even a rejuvenated Raheem Sterling could lead City's attack instead of Aguero on Saturday but Guardiola has some other big decisions to make.

New goalkeeper Claudio Bravo has played in plenty of big games for Barcelona and Chile but he has hardly trained with the rest of the City squad since he joined at the end of last month.

So it would be a gamble to hand him his Premier League debut in a game this big, especially in a derby atmosphere and against a team that pose as much of an attacking threat as this United side do.

The height and power of United striker Zlatan Ibrahimovic will make Saturday a big test for City's entire defence, not just their keeper.

As I said in my analysis on The Premier League Show on Thursday, United under Mourinho get the ball into the box far earlier and far more often than they were doing last season.

This season they have already made 53 crosses from open play, compared to 29 in the final three games of last season.

The reason they are doing that is their aerial threat, not just through Ibrahimovic but also the physical prowess of Paul Pogba and Marouane Fellaini when balls are delivered into the box.

They will play the same way against City - looking to get the ball out wide and then crossing it into the danger areas for someone to put their head on it.

With his goal against Leicester in the Community Shield, and then again against Southampton, it was Ibrahimovic who did that, and to perfection.

Ibrahimovic is great at reading the line of the cross and timing his jump above his marker, and then the accuracy and power of his header does the rest.

Ibrahimovic is not United's only in-form striker - the clamour for Mourinho to hand Marcus Rashford a start has increased after his hat-trick on his England Under-21 debut against Norway on Tuesday.

As I said on Match of the Day after Rashford came on to score an injury-time winner against Hull in United's last game, I don't think it will be long until that happens.

As a striker, when the manager picks other people then, when he gives you a chance, you have to take it.

That is exactly what Rashford is doing with all these goals and, when someone keeps on scoring like he does, it gets harder and harder to leave him out.

Rashford's time will come soon but, if everyone is fit for Saturday, it would not surprise me if Mourinho sticks with the same starting XI and uses him as an impact sub again.

Aguero's ban means City have to make at least one change from their last game but their approach will not change - Guardiola will play his usual possession game and try to stretch United.

In City's first game of the season, against Sunderland, we saw something new to the Premier League when he asked his full-backs to push into the centre of midfield to try to out-number their opponents, and both wingers stayed very wide.

When it works, like it did in the first half of their win over West Ham, City are very difficult to stop. The question is, will it work against Mourinho?

His United side will be quite content to sit back and try to hit them on the break and if City keep pushing their full-backs forward to flood midfield then they might just be open to counter-attacks.

We know now what United will do when they do get forward - put those balls into the box - but we don't know yet if City will be able to deal with them.

Alan Shearer was speaking to BBC Sport's Chris Bevan.

Credit: BBC Sport