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Leverkusen's team website announced that the defender has extended his contract with the club for another two years.
According to the new contract, the 23-year-old football player has committed to staying in the ranks of the German team until June 30, 2014.
Spanish-born Castro has worn the "Bayer" team's jersey 149 times in the Bundesliga. The full-back has also represented the German national team.