And The Sun have reported that Chelsea are considering activating the clause, in news that will surely concern the Manchester United hierarchy.
While Zlatan Ibrahimović has proved an undoubted success since arriving from PSG, United have struggled for goals this season, scoring as many goals as 11th-place Bournemouth and 19 less than Liverpool, who sit one place above them in the Premier League.
So the news that Chelsea are mulling over a bid for Griezmann will worry United, with both clubs possessing the financial firepower to meet his £86m release clause.
Both clubs will have been alerted to comments Simeone made earlier this week where he publicly confirmed the existence of a release clause in Griezmann’s contract.
Simeone was asked by the Spanish publication AS if Griezmann’s future at Atletico was in doubt and he replied: "Yes, because there is a termination clause. There is no security.
"That's what he told me [in the summer talks] - if you stay, I'll stay and I said yes, why would I not stay? And they began to work with the representatives for everything that had to be signed. And he stayed.
"To the players who have given me life I accompany them in the decisions that they make. But it is clear that for as long as he stays, the team and the club will continue to grow."