Van Gaal knows how difficult it will be to land either one of the midfield stars, and has been monitoring Gundogan after the 23-year-old returned to action for the reserves last week after a lengthy lay-off.
Dortmund have been struggling for form in the Bundeliga, losing four of their first seven matches, and Gundogan faces a challenge to win his place back in the starting line-up against the likes of Shinji Kagawa, Nuri Sahin and Henrikh Mkhitaryan.
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