Diego Costa admits he made a mistake when he threw a bib at Jose Mourinho and insists he has an "amazing" relationship with the Chelsea manager, who is backing his misfiring striker to re-discover his goal-scoring touch.
Mourinho confronted Costa over his performance during Chelsea's Champions League win at Maccabi Tel Aviv last month and benched the Spain international for subsequent Premier League matches against Tottenham and Bournemouth as tensions between the two became increasingly public.
Costa threw his bib in Mourinho's direction after he was dropped for the 0-0 draw at White Hart Lane and then sent out to warm up during the second half only to be told to sit back down with the rest of the substitutes.
The 27-year-old returned to the starting XI as Chelsea defeated Porto 2-0 at Stamford Bridge to secure a place in the Champions League knockout stage as winners of Group G.
The former Atletico Madrid man had a hand in the opening goal when his saved shot was deflected into the Porto net by Ivan Marcano and, after shaking hands with Mourinho when he was substituted in the 86th minute, the striker expressed regret for his earlier actions and admitted he needs to get back to his best form.
"I have to improve a bit," Costa told Spanish radio station Onda Cero. "The start of the season has not been good for me -- not in how I have played nor in goals.
"I know I have to be better to go to Euro 2016 with Spain. I have to work hard and fight, but I know I have time to improve and I hope I will.
"The bib [incident] is in the past. I made a mistake, but my relationship with Mourinho is amazing, we get on really well. There are things you need to control, but the bib thing was an impulse.
"The truth is Chelsea haven't been in a great moment, above all losing the other day at home [against Bournemouth]. Today it was important to win to make the fans happy and to recover our confidence."
Costa has scored just four times in 19 appearances for Chelsea in all competitions this season and after the match Mourinho admitted that the Spain international is less assured in front of goal last season while praising his effort.
"He could have scored two or three goals today," the Chelsea boss told his postmatch news conference. "His lack of confidence? Yes, clearly. But his attitude was very good and his movement was much better.
"The first goal was an own goal but his movement is great, the pass arrives. Last season he would score immediately. This season he couldn't."
Costa was also asked by Onda Cero about a return to Atletico in the future. Chelsea signed both Costa and left-back Filipe Luis in 2014, but the latter returned to the Estadio Vicente Calderon in the summer after struggling to make an impact.
"You never know, look where Filipe Luis is now," Costa responded when asked about a move back to the Spanish capital.
"Life takes plenty of twists and turns -- I always wish Atletico the best and I always follow them, support them from afar."