The Spain international only managed 12 Premier League goals as Chelsea finished 10th but has already netted twice under new boss Antonio Conte.
And Costa now looks set to stay – but it could have been a very different story.
“I wished I could go back to Atletico, I'm not going to lie," he told Spanish television channel MovistarPlus.
“Everyone knows what happened to me there [England], with the language, the weather and everything.
“But I can't complain because I'm a boy whom the fans love, at Chelsea they respect me.”
GETTY
Islam Feruz, Marcos Alonso and Diego Costa
Youngster set for Belgian loan spell
Isalm Feruz is reportedly set to sign a loan deal with Belgian side Royal Excel Mouscron.
The 20-year-old joined Chelsea as a youth player from Celtic at the age of 16 but has yet to make his senior debut.
But according to ESPN, he will have the chance to make an impact in Belgium’s top tier if he completes the temporary switch.
Feruz has already played senior football during loan spells at OFI Crete, Blackpool and Hibs.
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Chelsea close to £20m deal for Alonso
Marcos Alonso is on the verge of completing a £20million return to the Premier League, according to reports.
The 25-year-old arrived in English football from Real Madrid in 2010 when he joined Bolton.
He made 46 appearances for the club before joining Fiorentina but he also spent time on loan from the Italian club at Sunderland.
However, the Telegraph now claim Conte is finalising a £20m deal to bring the left-back back to England in the next 24 hours.