The former Athletic Bilbao midfielder joined United in the summer.
"I always had a lot of respect for United. I knew that it was one of the best clubs in the world and one of the most recognised and most followed - I saw the statistics for that," he told United Review. "It's a dream for me to be here but I have to work very hard if I want to be an important player at this great club.
"I have really enjoyed things and I am very happy, and I now understand how big the club is. In America on tour there were a lot of people supporting us and now in Manchester, when we play at Old Trafford and you see fans around the city, I understand even more."
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