The 100 million euros which Manchester City have offered for AC Milan's Kaka would be tempting for any club, even one whose owner, the Italian Prime Minister, Silvio Berlusconi, has a personal fortune of $9.4 billion.

But Milan's change of heart about a player previously described by Berlusconi as 'not for sale at any price' is not solely about money.

A number of footballing reasons are being put forward as to why the club would be prepared to sell a 26-year-old player who won the Ballon D'Or and was voted FIFA World Player of the Year just two years ago — and why Kaka would be ready to leave.

There are four main theories: (1) Kaka and fellow Brazilian, Ronaldinho, signed last summer from Barcelona, have not gelled as twin three-quarter players behind the striker in coach Carlo Ancelotti's favoured 4-3-2-1 formation; (2) Milan want to bring back the 22-year-old Joann Gourcuff, who is on loan to Bordeaux, and plan to play him in Kaka's role; (3) Milan intend to extend David Beckham's contract through to 2010 and want to use the Englishman in a more advanced role; (4) Kaka is no longer the golden boy at Milan, the mantle having passed to Brazilian striker Alexandre Pato and the tactical approach will be about getting the ball to him as quickly as possible.

Only the first theory really stands up. The mild-mannered and uncontroversial Kaka has gone public several times this season about his dissatisfaction with his duties since Ronaldinho arrived.

The subtext of Kaka's complaints is that he is expected to do too much donkey work — pressing and tracking back — to cover for the unfit Ronaldinho and consequently rarely finds himself in goal-scoring positions

Ancelotti will not abandon his system, so one of the players will probably have to be sacrificed and, although Ronaldinho is two years older than Brazilian teammate Kaka, it is unlikely to be the new signing who makes way.