Having made the Spain international aware that he no longer figured in their plans at the start of the summer, the Blues then saw the window close with no exit agreed.
With relations between player and club at a breaking point, Costa refused to return to west London as he remained AWOL in Brazil – the land of his birth.
He had made it clear throughout a protracted saga that a return to Atletico was his preferred choice, and he has now got his wish.
Is coming hooome, Is coming hooome— Antoine Griezmann (@AntoGriezmann) September 21, 2017
Griezmann is clearly delighted with the deal.
Goal revealed earlier on Thursday that an agreement had been reached for the want-away striker, with Atletico set to part with around £40 million.
Chelsea later confirmed that a deal had been done, although Costa will be unable to mark his return to the Spanish capital until January.
Europe’s leading clubs are unable to purchase players outside of windows, while Atletico are barred from registering new signings until the New Year as they work under a transfer embargo.
When they do get Costa back, they will be getting a forward who helped Chelsea to two Premier League titles during his time in England.
Part of the £32 million generated from his sale went towards landing Griezmann, with the France international having slipped seamlessly into the role of talismanic frontman.
He will now get the opportunity to work in tandem with Costa, as Atletico seek to make the 2017-18 campaign – their first at their new Wanda Metroploitano home – as memorable as possible.