A frustrating summer for the 29-year-old followed, with a return to Atletico agreed while the La Liga giants were working under the restrictions of a transfer ban.
Costa has, however, finally been freed to open a second spell in the Spanish capital and netted just five minutes after stepping off the bench in a Copa del Rey clash with Lleida Esportiu on Wednesday.
He is hoping there will be many more efforts to come, with the burly frontman determined to make up for lost time.
Costa told reporters after a goal-scoring bow: “Now I am very happy because I feel like a footballer again.
“It is great for me to play for Atletico Madrid again, the club are very important to me and I am very happy with this.
“I could not have asked for anything more on my second debut, to be back playing again and to have scored a goal is fantastic.”
A midweek outing for Atletico was Costa’s first since suffering defeat in the 2017 FA Cup final with Chelsea in May.
He did pick up a knock in the process of opening his goal account for his new club, with Atletico having announced that they will be carrying out medical examinations.
Costa took a blow to his right knee in finding the target against Lleida Esportiu, but was determined not to let a few bumps and bruises spoil his big night.