Diego Costa says bib row with Chelsea boss Jose Mourinho is behind them as he vows to turn awful start to the season around

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Chelsea firebrand Diego Costa claims he has an 'amazing' relationship with Jose Mourinho even after the striker threw a bib at his manager following his recent exclusion from the side.

Costa started for the first time in three games against Porto on Wednesday night and had a hand in both goals as Chelsea secured a Champions League last-16 spot with a 2-0 victory.

Mourinho has struggled to coax Costa into replicating the form that saw him hit 21 goals in his debut season at Stamford Bridge this campaign but stuck by the striker until his recent run on the bench.

Chelsea star Diego Costa says he and manager Jose Mourinho have put their recent squabbles behind them

Costa was seen throwing a bib in the direction of his manager when Chelsea drew away at Tottenham

But Costa was able to make an impact against Porto, having a hand in both goals as Chelsea won 2-0

Against Tottenham at White Hart Lane last month, the 27-year-old was seen throwing a bib in his manager's direction after it became clear he was not going to be called upon as a substitute.

But Costa says the pair are more than happy working together despite the problems that have come with Chelsea's disastrous title defence this season.

'The bib [incident] is in the past,' Costa said. '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.'

Costa has just four goals to his name this season after returning from his summer break out of shape and overweight.

His form contrasts with that of the striker who set the Barclays Premier League alight in the early stages of the last campaign - in which he had hit 11 goals by this point.

Costa takes his bib off before flinging the garment over his right shoulder during the draw with Tottenham

The bib sails behind Mourinho's right shoulder but the Chelsea boss seemed oblivious as it flew to the ground

'I have to improve a bit,' Costa said. 'The start of the season has not been good for me - not in how I have played nor in goals. 

'The truth is Chelsea haven't been in a great moment, above all losing the other day at home (against Bournemouth). Today (against Porto) it was important to win to make the fans happy and to recover our confidence.'

With Costa struggling to adapt to life in England and having difficulties with the language, speculation has persisted on the continent that the Brazil-born forward would like to move back to former club Atletico Madrid.

Costa would not rule out returning to Atletico Madrid one day after speculation linked him to his former club

Costa celebrates Chelsea's clincher with Willian and Eden Hazard after an all-action performance

Costa stoked the fires of the rumours, admitting to Spanish radio station Onda Cero: 'You never know (about a return to Atletico Madrid), look how well Filipe Luis is doing now.

'Life is full of surprises – I always wish Atletico the best and I always follow them and support them from afar.'

Mourinho confirmed his happiness with the striker after an all-action performance upfront that included a clash with Porto goalkeeper Iker Casillas that earned Costa a yellow card.

The Chelsea boss was seen rowing with Costa in last month's win at Maccabi Tel Aviv and criticised his movement as the lone centre forward, but he found improvement in that regard on Wednesday.

Chelsea's Brazilian midfielder Ramires posted this photo from the dressing room with Costa and Kenedy

Asked if Costa was lacking confidence, Mourinho said: 'It's clear, but what is also clear is his effort, commitment and great movement, which is something he hasn't had in the last couple of months. Tonight it was great.'

Ivan Marcano deflected the ball into his own net for the opener at Stamford Bridge after Casillas had saved from Costa, before the Brazilian-born striker passed to Eden Hazard to set up Willian's clincher.

'The first goal was obviously an own goal but his movement was great when the pass arrived,' Mourinho said. Last season he would have scored immediately but this season he couldn't.

'He could have scored two or three goals today. There is a lack of confidence, clearly, but his attitude was very good and his movement was much better, so goals are coming.'

Porto defender Maicon looks to drag Costa back as he is drawn into a row with goalkeeper Iker Casillas