Castillo's agent has claimed the forward is on the verge of joining City but Shakhtar president Rinat Akhmetov insists a deal is a long way from completion.

Akhmetov outlined to the club's official website the terms which would allow the player's departure from the Ukrainian club.

"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.

"We will see in a year whether to bring him back to Shakhtar or if we sell him.

"The price could be 20, 30, 40 or 50 million euros."

Castillo became Shakhtar's record signing when they bought him for £12.5million from Olympiacos in August but he has made just eight league appearances and has yet to find the back of the net.

And Akhmetov believes the player, who can play in midfield or as a striker, needs to alter his mentality to prove he is worth his hefty transfer fee.

"He was a star at Olympiacos and he came here as a star," he added.

"He thought that because we paid 20 million euros for him his place was assured. He forgot that he had to win it."