Supporters on the club's official Facebook page posted questions for Juan...
You've settled into life now at Old Trafford, but how did it feel to step out at our stadium as a United player for the very first time?
There were so many feelings. It's difficult to explain them with words. I played, I felt happy, we won [against Cardiff] and I felt the love from the crowd. It was an amazing day with lots of emotions and I'll always remember it.
I saw you looking around the Manchester United museum recently – how impressed were you with what you saw?
Everyone knows about the history of this club but it's only when you see it properly and see the trophies that you realise how astonishing it is. For me, it's always been good to know about the history of your club and I think this one has the best history in the country.
Who is the best cook – you or your good friend David De Gea?
I think we are both the worst! [Laughs]. I would like to get better. My friends have told me cooking is quite relaxing so I will try to learn more.
Who was your football idol when you were younger?
[Roberto] Pompei is one. He was a midfielder for Real Oviedo, who I supported and still support. He also played for Argentina. There was Pablo Aimar, who played for Argentina as well, and when I was at Real Madrid I loved watching Zinedine Zidane. He played with so much elegance.
What is your big passion outside football?
I enjoy many different things. I like to read and watch movies and TV box-sets if I am away with the team. On a day off I like to explore places around the city or villages nearby to my house. I'm a curious person. I like to know about many different things.