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.
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.
“Dear Atletico fans, today I only have words of gratitude for you,” Partey wrote on his Instagram account.
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Querida afición rojiblanca, hoy solo tengo palabras de agradecimiento con vosotros. Desde hace ya varios años, el Atlético de Madrid ha sido mi casa y una parte de esta familia siempre estará conmigo. Quiero dar las gracias al club por la confianza depositada en mi desde el primer día , pero sobre todo, quiero daros las gracias a vosotros, a esta maravillosa afición que me acepto desde el primer momento y que ha demostrado que está tanto en las buenas como en las malas y que verdaderamente nunca deja de creer. El atlético de Madrid no es solo un club, es una familia. Gracias ♥️
“For several years now, Atlético de Madrid has been my home and a part of this family will always be with me.
“I want to thank the club for the trust they have placed in me from the first day, but above all, I want to thank you and your wonderful support that accepted me from the first moment and that has shown that they are with me in both the good times and the bad.
“They truly never stop believing. Atlético de Madrid is not just a club, it is a family. Thank you.”