The Ghanian midfielder appears to be on the way to north London as the Gunners agreed to pay his £45m release clause.
And Spanish outlet Libertad Digital have reported that it has even caught Atletico manager Simeone by surprise.
The Argentine was “so sure” that Partey would stay that he has been talking to Lucas Torreira – who is set for a loan move to the Wanda Metropolitano in a separate deal – about a midfield pairing.
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And it saw the boss mention the Ghanian in tactical discussions with the outgoing Gunners star, starting the midfielder regularly since the start of the 2020/21 campaign.
With the 27-year-old now set for his £45m move to Arsenal, it has left the Atletico boss “very angry”.
Partey will be bringing an end to his career in Spain after five years, making 188 appearances for the La Liga side.
He also boasts Champions League experience, helping Atletico to the quarter-finals last year while reaching the final in the 2015/16 campaign.
Arsenal are also paying Partey £260,000-a-week in a four year contract with an option, including a £2.5m signing-on fee and 10 per cent agent commission to complete the staggering package.
And the numbers involved left Gunners legend Paul Merson “falling out of his chair” over the midfielder.
“I think he’s a top draw player,” Merson said on Sky Sports.
“I nearly fell off my chair, £45million, I don’t think that’s a lot of money, at all for the quality of player you are getting here.
“The one thing he brings as well. Discipline. He has played at Atletico Madrid, who are one of the most disciplined teams in Europe and he would do that.
“He’s not a midfield player who goes running all over the place and you are thinking ‘where has he gone?’. He is very disciplined. I think he would be a great signing.”
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