The 24-year-old explained that he wants to repay his management's faith in him after the Spanish club turned down a £25.5 million offer from the Red Devils during the summer
As Goal reported in August, the La Liga outfit rejected a £25.5 million bid from United for the 24-year-old on the eve on deadline day.
The Spaniard indicated he was flattered by the English team's interest in him but insisted he is not keen on leaving Athletic, which he sees as the "perfect place" for him.
He told Canal plus Spain: “I appreciate both Manchester United’s interest in me and the fact that I am considered so important to Athletic that they did not accept any bid for me.
"That means that Athletic values me above money and trust in me more than money for our current project.
"I’m right where I want to be. I’m not a player who wants to change teams, I’ve taken root at Athletic and it is the perfect place for me to be.”
Manchester United have been struggling in the league this season and currently find themselves in ninth position, with new boss David Moyes coming under fire for a lack of successful business during the summer.