Sven Goran Eriksson remains confident that Nery Castillo will prove to be a good acquisition for Manchester City.

The Mexican midfielder has made little impact in the Premier League since his arrival on loan from Shakhtar Donetsk in January, and has made just four starts for the club.

He has struggled to adapt to the physical nature of the game in England and has been blighted by niggling injuries.

"We believe that he will be a great player for us, as he was at Olympiakos and as he has been for Mexico," Eriksson told the Manchester Evening News.

"I believe in him, absolutely. But he has to be stronger and fitter."

Castillo is determined to earn a permanent move to the City of Manchester Stadium when his deal runs out at the end of the year, and Eriksson remains hopeful that he will be able to call upon the Mexican in City's remaining fixtures.

"When he came, he was not 100 per cent fit. He has been unlucky," said the Swede.

"Since January, he has missed 50 per cent of our training sessions, so he's still not fit.

"But I hope and I still believe that he will get better and that he will play this season."