The prospects of Kaká making a world-record January transfer from Milan to Manchester City appeared to be over last night after a highly placed source close to City's owner claimed widespread reports of a £100m bid were "absolutely ridiculous". Kaká himself is also understood to be deeply reluctant to join City – whatever the fee and salary package – unless there is a change of manager.

The adviser to Sheikh Mansour bin Zayed Al Nahyan, City's billionaire owner, told Observer Sport from Abu Dhabi last night that media coverage of City's offer for the Milan player, plus reported £500,000-a-week wages, was wildly unrealistic – giving credence to growing rumours in Italy that the story has been hyped up by Milan owner Silvio Berlusconi, in an attempt to earn good publicity when no move materialises and Kaká stays at the San Siro. First reports of the "£100m" bid appeared on a website owned by Berlusconi.

"The reports are absolutely ridiculous and so far wide of the mark it's unreal," said the source, who claimed that while contact had been made with Milan, any deal for the former Fifa World Player of the Year would involve an offer nearer to £50m than the reported £100m. "Kaká would command a price around that of previous world-best players. But at the moment it is difficult to pick an exact number."

Luís Figo and Zinedine Zidane, who also won the Fifa award, were bought for £38m and £46m respectively, with the latter figure representing the current world record for a transfer, which was paid by Real Madrid to Juventus for the French midfielder in 2001.

The adviser also claimed that, contrary to reports, negotiations have still to reach an advanced stage for Kaká, that no formal contact has been with the player, and that a defining element of financing any deal would have to include intellectual property rights to make it commercially realistic.

"A hundred million, in pounds or euros, is ridiculous," he said. "It doubles the previous record for a transfer and, in the current economic climate, how could there possibly be a return on that or a salary of £500,000 a-week? You could do so much else with that amount of money. And, whatever happens, there would be no lump sum payment: payments would be over time.

"You have to remember also that the player has not even been spoken to by us – he is simply one of a list that interests Mark Hughes. We merely said, 'Ok, this might be nice.' It's a process like viewing a house. If you like what you see, then you take it on a stage. It should be remembered that Manchester City's owner is an intelligent man. He will not just throw money at anything. And Gary Cook [City chief executive] was formerly at Nike so knows all about intellectual property rights."

David Beckham's lucrative remuneration packages at Real Madrid and Los Angeles Galaxy – he is thought to earn £25m a year at the US club – were financed by earnings from his intellectual property including image rights. Kaká, a devoutly religious man whose highly respectable image has already attracted blockbuster deals with Armani and Adidas, would be sure to generate millions in off-field earnings, which would be a complex part of any proposed deal.

But regardless of the financial obstacles, Kaká's reluctance to join a club of City's stature also appears to have hardened. The Brazilian was shown plenty of support by the 65,000 crowd at the San Siro last night, when he played impressively in Milan's 1-0 win over Fiorentina, a game in which Beckham lasted 81 minutes before being substituted.

Fans' banners ranged from the supportive ("Kaká, grow old with us") to the dismissive ("I belong to money," a play on his T-shirt slogan "I belong to Jesus"). His car was mobbed as he left the ground by fans imploring him to stay. Berlusconi appeared to play up the chances of Kaká leaving when he said: "It is very difficult to make someone stay after they've seen such wages." But "such wages" might be on offer only in reports generated by Berlusconi's own website.

Beckham, asked if he had talked to Kaká about the possible move, said: "Ricardo doesn't need my advice. He's a man, he's a great player and one of the nicest people you will meet. He will decide what he wants to do. But he does love Milan. It is not all about money."

While City still expect to meet Kaká's father Bosco Leite this week, sources close to the player suggested last night that Kaká would want City to appoint José Mourinho "or a manager of close calibre" to convince him he would be moving to an "appropriate platform", and that City would be capable of rapidly establishing themselves as "one of the best eight teams in the world".

Kaká is in regular contact with Brazil team-mates Robinho and Elano, who have found Hughes hard to work with at Eastlands, the latter complaining publicly about a lack of communication from the manager. Kaká has also told advisers he would not consent to a move from Milan unless the club had a coherent strategy to challenge for the Champions League trophy. The 26-year-old would further seek assurances that Sheikh Mansour will neither lose interest in City and walk away nor significantly reduce his investment in the club, as Roman Abramovich has done at Chelsea.

Kaká's long-term adviser Diogo Kotscho told Observer Sport: "We have to see a good project, a winning project, for any club to be eligible to have a player like Kaká. We have to be convinced that Manchester City can turn themselves – in the short term – into one of the best eight teams in the world."

Bringing Mourinho to Manchester would help, and City are understood to have made moves in that direction. According to one of the former Chelsea manager's closest advisers, the sheikh's representatives contacted Mourinho's camp shortly after their September takeover to offer him the City job with immediate effect. Mourinho swiftly rejected a proposal that would have doubled his already lucrative salary at Internazionale. He has, however, monitored City's progress since and such is his desire to return to English football has not ruled out the possibility of joining them next season.

Mourinho's conditions would be similar to Kaká's – the promise of a front-seat role in a "very great project" coupled with a financial offer that would be extremely difficult to resist. Even the combination of both, however, are not guaranteed to bring City success in the pursuit of the pair with the political turmoil at Real Madrid another significant complication.

Ramon Calderon's resignation as Real president over allegations of vote rigging has opened the path for candidates for the post to base their election campaign around the pursuit of Kaká. The player himself would prefer a move to Madrid, Manchester United or Chelsea –should Abramovich resolve his financial difficulties.