The Primera Liga side have paid eight million euros for the services of Mosquera, who has penned a five-year contract with the reigning two-time UEFA Cup champions.
The 26-year-old was unveiled to the Spanish media at a press conference at the Ramon Sanchez Pizjuan stadium on Friday, and said: "It is a dream to play for this team. I am extremely happy to be at a club which has won so much over the last few seasons."
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