#2 Lars Bender
Bender was very close to joining Arsenal last summer, but Leverkusen's qualification for the Champions League deterred him from seeking a move elsewhere. This summer might test his ambition again, especially if Leverkusen fail to qualify for the Champions League.
Leverkusen are currently in a very tight battle for qualification with Schalke, Gladbach and Augsburg. Should things go awry, they might not be able to hold onto their star man. Bender is known to have quite a few admirers in Europe, with Arsene Wenger, in particular, being a very big fan. Barring Arsenal, he is known to have generated interest from the two Manchester clubs too.
Keep an eye out for him for he might just be next summer's big money transfer.