After a lot speculation bordering the strikers long term, Costa created the change to Stamford Bridge after Chelsea activated his purchase -out clause of 32million.
The twenty five - yr - aged invested 4 years with Atletico but truly arrived to prominence last season as he helped Simeone's guys to clinch the La Liga title and get to the Champions League last, netting 36 objectives in all competitions together the way.
Costa has penned a profitable five - 12 months offer with Jose Mourinho's facet and Simeone spoke of his appreciation for the Spain international's endeavours for the duration of his time at the Vicente Calderon.
"I am usually going to be grateful to the players that give all their ideal. He experienced excellent performances even though he was with us," he said.
Atletico have continually experienced to market their leading gamers in latest yrs, with Costa just the newest in a record that consists of the likes of Sergio Aguero, Fernando Torres, Diego Forlan and Radamel Falcao.
Even so, Simeone is optimistic that yet another goalscorer can be unearthed to fill the boots of the person they initially signed as a again -up alternative from Valladolid.
He said : "Aguero remaining and many acquired frightened, Falcao arrived and the team received what it received. Then Falcao still left and it seemed like the team couldnt strengthen. Costa arrived and the team kept on rising.
"Atletico has constantly taken care of each change incredibly nicely and we expect this time to be the very same."