Atletico Madrid striker Sergio "Kun" Aguero stunned Spanish football late on Monday night by officially asking for a transfer from the club.

The 22-year-old announced his decision on his official website and on his Twitter account after he and his father had held a meeting with club directors Miguel Angel Gil and Enrique Cerezo in the Vicente Calderon Stadium earlier in the day.

Aguero insisted that he had taken his decision because he wanted to continue to develop as a player, rather than for the desire to earn more money.

"I am about to celebrate my 23rd birthday and I have everything ahead of me and I want to say that it is not an economic question, but strictly a sporting one. I have thought a great deal about the decision and I have to be true to myself," reads Aguero's statement.

Atletico have had a disappointing season, finishing the campaign in seventh place, after they had kicked off with hopes of qualifying for next season's Champions League. Nevertheless Aguero's decision is slightly surprising given that he decided to sign a new contract with the club just a question of months ago, although the new deal saw his buyout clause reduced from 60 million Euros down to 45 million Euros.

Atletico insist that they will not negotiate a sale and that any team wishing to buy Aguero will have to pay that clause. Should a Spanish club wish to sign Aguero, and FC Barcelona and Real Madrid have both been mentioned as possible destinations, taxes would take the total price to the player to around 70 million Euros.

English Premier League sides Manchester City and Chelsea could also be Aguero's destination and it is unlikely Aguero would have announced his intention to leave Atletico Madrid unless he had a firm offer from somewhere.

It is hard to imagine him joining Atletico's neighbors, Real Madrid in an act that Atletico fans would see as a betrayal of their club, while Barcelona's economic situation could rule them out of any move for the player, unless it involved including other footballers in a part exchange.

Aguero joined Atletico from Argentinean side Independiente in 2006 and has made over 200 appearances for the club, scoring 101 goals. On Saturday he scored a brilliant hat-trick in Atletico's 4-3 win away to Mallorca in what now looks as if it was his last appearance for the club.