Both sides will be going for a win - for many reasons.
Look at the honours list for any big English club. They include the Community Shield. Football is about silverware and it is not some tin pot trophy, but a game which players take seriously. I know I always did.
You earn the right to win the Community Shield — or Charity Shield as it was in my day — by winning the league or FA Cup. While you would not be as disappointed to lose the game as you would a European, FA or even League Cup final, I do not buy into the view that it is a glorified friendly.
The reasons for winning run deeper this year. Whereas United play in the Community Shield almost every August and Sunday will be Ryan Giggs 15th, Manchester rivals City don't.
This will be a game between the two sides who I expect to finish first and second in the Premier League this season. Whoever wins it can put down a marker for the other side.
I have just been on United's pre-season tour of America and know what the players are saying.
They are not talking about revenge because City knocked them out of the FA Cup in the semi-final at Wembley, but of showing the country that they are the league champions, the best team in England and the best team in Manchester.
That said, the Community Shield is a notoriously poor guide to the season ahead. I played in a United side which lost 3-0 at the start of the treble-winning year.
We lost to Arsenal the following year and yet still won the league by a mile. Yet Sunday is still a big game.
I think the league is United's to lose and they looked impressive the tour of America, especially against an admittedly understrength Barcelona.
Sir Alex Ferguson has tweaked his squad, bringing in talented young players such as defender Phil Jones, goalkeeper David De Gea and winger Ashley Young, to replace the retiring Edwin van der Sar, Paul Scholes and Gary Neville.
Maybe he will add more players and Wesley Sneijder would be a great addition, but I was really impressed with the youngsters Daniel Welbeck and Tom Cleverley on tour.
United's greatest asset is their team spirit and winning mentality. They are united.
Can the same be said of City?
City will improve again and finish second in the league, but they have a lot of names they wish to offload and that's not good for team spirit.
They have some great players and I like their new signing Sergio Aguero.
He shone in Spain, but the Premier League is totally different, especially if he is asked to play alone up front as City tend to play.
That would mean no Carlos Tevez and his situation needs clearing up.
Tevez, who will miss the Community Shield after being granted an extended holiday to recuperate from the fatigue of playing in Copa America, is not afraid to speak his mind and that causes problems.
He doesn't jump to anyone's tune but he is a top player, no doubt, and one who scores goals.
But will he play if City can't sell him in the transfer window?
Will the fans push for Tevez to play if City are not scoring and Aguero doesn't start off well?
Will Roberto Mancini then play him alongside Aguero so that he has a foil like he had with Diego Forlan at Atletico Madrid?
And then we throw Mario Balotelli, another striker, into the mix. He has got talent, but I'll be diplomatic and describe his character as being different.
Mancini needs to get control of the situation. He seems to be a manager who likes to dominate his players.
It is his way or no way and if you don't agree to that you are sidelined. I sense he will need to be a bit cuter with Balotelli.
City will be stronger, partly because I'm not convinced that the other rivals can win the league. Chelsea have a bright young new manager but an ageing team. Liverpool are buying young, mainly British, players. Winning the league for the first time since 1990 will be beyond them this season, but they are improving.
Stuart Downing and Luis Suarez are very good signings, although I can't understand why they paid so much for Jordan Henderson, an average player.
Arsenal's reluctance to buy top quality means that they won't win the league and Arsene Wenger will face more pressure as the focus shifts to the Manchester clubs.
Whoever wins on Sunday will set down their marker for the season ahead. I can't wait.
Andrew Cole's column is written with the assistance of European football correspondent Andy Mitten.
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