It was reported by Diario AS that the club are angry over how the deal was conducted with neither the Gunners nor the player himself informing the club of the transfer.
— Atlético de Madrid (@Atleti) October 5, 2020
Instead, Atleti only were informed of the deal by La Liga – who received the midfielder’s €50m release clause in form of payment from Arsenal with the player’s legal representative arriving at the league’s HQ to legally sign the document which would complete the transaction.
Atleti are unable to stop a transfer if his release clause is deposited at La Liga headquarters, with the selling club not involved in the process.
The Ghanaian star has been a member of Atleti’s first-team squad since the 2015-16 and his exit to North London will come as a serious blow to the club, who had been intent on maintaining him for this campaign.