KIEV, Dec 17 (Reuters) - Shakhtar Donetsk's president is willing to loan the club's most expensive acquisition - Mexican midfielder Nery Castillo - but for no less than five million euros a year, the club's Web site said on Monday. Castillo's agent told Mexican television on Friday that an agreement has been struck with Manchester City to loan him out, but club president Rinat Akhmetov said the offer of a million euros with an option to buy Castillo was rejected as too low. 'A one-year loan -- five million euros and there will be no options, meaning a right to buy (Castillo),' said Akhmetov, the country's richest man. 'If Castillo finds his game ... then in a year we'll decide whether to take him back to Shakhtar or sell. And the price could be 20, or 30, or 40, or 50 million euros,' he said. Shakhtar bought the Mexican last summer for 20 million euros in one of the most expensive buys in post-Soviet club history. But the player did not impress, playing just eight home league matches and failing to score any goals. 'He was a star at Olympiakos, and he came here like a star... Probably, he thought that if we paid 20 million euros for him, his place in the team was certain. But he forgot that this has to be won,' Akhmetov said.