#8 Juan Mata
Juan Mata currently signed to Manchester United F.C acting as a midfielder, began his career with Real Madrid, emerging as a star from their academy in 2006 and playing 39 times for their B team scoring 10-times.
But, he never made it big in Spain and didn't make a single appearance for their major side. Also, there were some reports, interest from Barcelona for Juan, it came close but never really happened.
The move wasn't successful, though Mata stayed in Spain, it was at Valencia, whom he joined instead of the Catalans. He totally shined at the Mestalla, scoring 33 goals in 129 matches for The Bats before finally moving to Chelsea in 2011.
According to The Guardian, there were some interest from Barca for Juan during, La Liga club, searching for a creative midfielder. The deal between him and Barcelona was quite strong, and Mata was constantly spoken of as a future Barca star.