Now the ban has been served, rumours have again been circulating regarding Griezmann's possible departure, with Barcelona reportedly favourites to pay the 26-year-old's £88.4m release clause, despite the striker's underwhelming form in the first half of this campaign, where he has only been able to register five goals.
"I've waited a long time for this day, I'm exhausted of training and I need to play", Costa said on Sunday.
"I want to thank the club for the effort they have made to bring me back", Costa said, in comments reported by Marca. "I'm exhausted of training".
Atletico's ban on registering new players due to the illegal transfer of minors expires on Monday, meaning Costa could make his debut against Lleida Esportiu in the Copa del Rey on Wednesday, with his first league appearance set for Saturday at home to Getafe.
On Sunday, Costa said he bore no grudges against anyone at Chelsea despite perhaps never fully settling in London.
I didn't learn English, which is a bit of a shame.
"I'm in much better shape than when I arrived, I've prepared well and worked hard and I'm ready to help the team and score goals".
"Chelsea is a great club and I only have good memories".
"It's true that there are players of great quality and at the end of the day it is the coach who will decide".
Atletico also unveiled the signing of Vitolo from Sevilla in a deal that saw the Spain winger trigger his €37.5 million release clause.