The Gunners slumped to a 4-3 defeat to Liverpool on Sunday, and their defensive frailties weren't much of a surprise given that inexperienced youngsters Calum Chambers and Rob Holding were forced to start the game.
Laurent Koscielny was rested having returned late from Euro 2016, whilst other centre backs Gabriel Paulista and Per Mertesacker are both missing through injury – meaning Arsene Wenger needs to bring in another centre back before this month's transfer deadline.
Sporting Braga's Nicola Stoiljkovic in action against Fenerbahce's Simon Kjaer
Sky Sports report that a move for Valencia star Shkodran Mustafi is dragging on, and whilst the German international wants to join Arsenal, Gunners boss Wenger is now eyeing up potential alternatives.
The report names two players Wenger is looking at, as Sky Sports claim that Bayer Leverkusen's Omer Toprak and Fenerbahce star Simon Kjaer are both on Arsenal's radar.
27-year-old Toprak has made 170 appearances for Bayer Leverkusen following a 2011 switch from Freiburg, but much to the concern of Arsenal fans, he's had his fair share of injury problems in recent times.
With three injuries last season, Toprak missed a number of games and may only add to Arsenal's problems injury-prone defenders, though when fit the Turkish international has proven himself to be one of the top centre backs in the Bundesliga.
Denmark's Simon Kjaer looks dejected
If Wenger doesn't go for Mustafi or Toprak, it's suggested that he could make a move for Danish international Simon Kjaer, who is currently playing in Turkey with Fenerbahce.
Kjaer, also 27, has been highly-rated for years now, and has often been linked with moves to the Premier League during spells with Palermo, Wolfsburg and Lille, but he's spent the last year in Turkey.
A strong, powerful centre back with great aerial ability, Kjaer has 59 caps for Denmark and could be a smart option for Wenger – but he certainly appears to be behind Mustafi on Arsenal's list of defensive targets.