Manchester United could be set to make a significant addition to their squad, with reports suggesting that the Premier League champions are ready to make a move for Spanish playmaker Koke.
And the same reports suggest that Manchester United - who, along with Premier League rivals Liverpool, have been linked with a move for Koke in recent weeks - are ready to make their move and activate that aforementioned clause.
The 21-year-old - who has already earned seven senior international caps under Vicente del Bosque - has been impressing for Atletico, netting three goals and recording eight assists in 15 La Liga appearances so far this season as Diego Simeone's men seek to dismantle the traditional Real Madrid-Barcelona axis that has dominated Spanish football for so long.
The Rojiblancos, who secured a comfortable 2-0 victory over Elche at Manuel Martinez Valero on Saturday, currently sit second in the La Liga standings - behind Gerardo Martino's Barcelona only by virtue of a slightly inferior goal difference.
Manchester United's supposed interest in Koke would certainly not come as much of a shock, with David Moyes clearly desperately in need of improving his side's creative input from midfield.
Liverpool boss Brendan Rodgers, meanwhile, would presumably be disappointed to lose out on such a promising player - particularly to fierce rivals Manchester United.
However, Liverpool have begun the season in impressive fashion in an attacking sense, and it could be argued that, following Sunday's disappointing 3-1 defeat to newly-promoted Hull, Rodgers needs to focus upon bringing defensive reinforcements to Anfield.