The Argentine moved to the Spanish outfit during the summer and introduced himself to the Champions League in some style against Bursaspor, slamming home from 30-yards.
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Speaking to Spanish website AS.com, the 25-year-old revealed that the game against the Red Devils will allow him to reach goals he once thought were impossible.
He said: “If I look back to three or four years ago, I remember I was on a 15-hour bus journey to play a third division match in France.
“Now, I fulfil all of my dreams at once; to play with Valencia, to play at the Mestalla, to be in the Champions League, and to face Manchester United. That’s crazy!
“There is nothing bigger than playing against a power like Manchester United. I have fought a lot and waited so long for this moment.”
Meanwhile, Costa’s team-mate and club captain David Albelda is confident Valencia can defeat United on the back of a 4-0 win over Turkish champions Bursaspor.
“For me there are no doubts,” Albelda told Sky Sports. “We are playing in Valencia and at this moment Manchester United are not favourites.
“I don't dispute that the English club are favourites for the group, but Valencia want to win.
“For Valencia this match is similar to playing Barcelona or Real Madrid. We are hosting a historical club at our stadium."
By Luke Nicholls
