Manchester United ace Robin van Persie says he's grateful to have worked with manager Sir Alex Ferguson this past season.

Ferguson announced his retirement last week.

"To be able to work with Sir Alex for one year, it's been a massive year. It's been an unbelievable year which I will never forget. He's an unbelievable manager, maybe the best ever. But he's an even greater person. I'm really honoured to have worked with him," said Van Persie.