Calum Chambers' move to Aston Villa highlighted Arsenal's inability to effectively sell fringe players.
The Gunners have been maligned for their transfer dealings in recent years, often accused of allowing players to run down their contracts before allowing them to leave for a cut-price, or even for nothing.
On Thursday evening, Chambers was allowed to complete a move to Villa for an undisclosed fee, with The Telegraph reporting that it was a free transfer.
The 27-year-old was into the final six months of his contract at the Emirates Stadium, although the north London club were thought to have an option to extend his deal by 12 months.
However, Arsenal could have cashed in on his services for a whopping £20million back in August 2017 when various reports claimed that Leicester City had seen a hefty offer for his services rejected.
Mikel Arteta's side made another similar transfer mistake that has been high highlighted this month, with the decision to convince Hale End academy graduate Ainsley Maitland-Niles to stay 18 months ago looking similarly damaging.
The England international was in talks with Wolves, who were reportedly ready to pay £20m before Arteta eventually persuaded the versatile star to stay at the club.
Still, Maitland-Niles has been used sparingly since, as Arteta has preferred the likes of Takehiro Tomiyasu and Cedric Soares at right-back whilst also picking Granit Xhaka, Thomas Partey and Albert Sambi Lokonga ahead of him in central midfield.
The lack of game time meant that the 24-year-old was desperate to leave this month before sealing a move to Serie A giants AS Roma until the end of the current campaign when he will have just 12 months remaining on his contract with the club.
These two mistakes alone could cost Arsenal up to £40m in transfer windfall, a huge amount of money to waste on players that have rarely been consistent starters for the north Londoners.
