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Borussia Dortmund has one of the strongest, up-and-coming defenders on their hands in the form of the Serbian known as Nevin Subotic.
Being named to the Team of the Year of the first half of the 2008-2009 season in the Bundesliga, Subotic is a hard-tackling defender that would add that edge of aggressiveness to the Gunner back line that could really spark a raid of the top four later on in the season.
He would be a hard signing, though. Chelsea chased him throughout last year's winter transfer window and was turned down after they submitted a formal bid of £17.5 million in mid-January.
According to talkSPORT, however, he would leave the German side if an English club were to come calling again.
Subotic was a part of the United States youth squad, up until U-20, when he only made two appearances for the United States. From there, he declared his loyalty to his Serbian birth country and joined the Serbian senior national team in 2009.