Mikel Arteta faces some challenges when it comes to constructing his Arsenal defence at the moment. Arsenal face some testing fixtures in the coming days, as they will take on Shakhtar Donetsk in a Champions League clash on Tuesday evening, before welcoming Liverpool to the Emirates Stadium for a Premier League showdown on Sunday. Mikel Arteta has suspensions and injuries to cope with when it comes to his team selections for these games. Martin Odegaard and Bukayo Saka are both struggling, with the former ruled out entirely for the visit of Shakhtar and the latter a doubt. Meanwhile, the Gunne…