But that’s what happened last night as the Stamford Bridge striker returned to Madrid to catch up with the Atletico Madrid boss before he joins up with the Spanish national team.
Costa has been in very impressive form for the Blues this season, scoring nine goals and assisting three more in the English Premier League.
That’s contributed to a strong start for Antonio Conte’s men too, with the 5-0 win over Everton at the weekend taking them up into second in the table just a point off leaders Liverpool.
So the last thing anyone at Chelsea will want to see is Costa reuniting with Simeone.
The Spaniard spent the summer flirting with a return to Atletico and it actually looked like he was going to leave Chelsea at one stage before the deal fell through.
But he’s still close with his old manager – and shared a picture of their dinner meeting on Instagram last night:
So Costa and Simeone are definitely still close – and that means links with a return to Atletico Madrid probably won’t go away despite the strong form of the Spanish international at Chelsea.
He’ll now join up with Spain for their upcoming World Cup qualifier against FYR Macedonia before taking on England in a friendly at Wembley.