Arsenal are plotting a move for Bayer Leverkusen star Omer Toprak as a potential alternative for Mustafi after still not being able to agree terms with Valencia according to BBC journalist David Ornstein.
Toprak was years of Bundesliga, Champions League and international experience for Turkey under his belt and did recently hint that he would consider a move.
The report claims that United scouted Toprak all season and that they were plotting a move for the experienced defender.
Arsenal are however, in a defensive crisis following injuries to Per Mertesacker and Gabriel. Meanwhile Laurent Koscielny missed the Gunners opening Premier League game of the season against Liverpool and he is a doubt against Leicester City next week.
Toprak, Hakan Calhanoglu and West Ham loanee Gokhan Tore were involved in an altercation last year which resulted in a gun being pulled on the Bayer duo.
Tore was reported to have had a fight with a friend of Toprak while a friend of the Hammers winger held a gun to both Bayer players.
The incident sparked outrage but Terim has decided to forgive Tore at what seemed the expense of Toprak and Calhanoglu.
Calhanoglu has accepted to return to the national team fold unlike Toprak.