"Nobody doubts his qualities but he is still young and needs to find consistency because when you play for teams like Juventus, Real Madrid and Chelsea you have to be consistent".
Recently returning to London, the Spanish international hasn't relented in the pursuit of his dream move to the Spanish capital.
That would suit Atletico; they cannot register the transfer until 1st January 2018 so have three months to work on Costa's match sharpness with the target of unleashing him on La Liga after the Christmas break. The transfer window opens until then and Diego Siemeone's side are currently banned from signing any players until then.
And although he has found his feet relatively quickly, he admits that it has not been easy for him to adapt to the rigours of the Premier League, as well as a whole new life in England.
Earlier on Tuesday, the Sun reported that Costa had returned to Spain in an effort to get talks going.
That leaves Costa four months to prove himself to Spanish coach Julen Lopetegui ahead of next summer's World Cup finals.
With the two-time Premier League title winner deemed surplus to requirements, Antonio Conte opted to invest £70 million in the highly-rated 24-year-old. In addition, he has scored 20 league goals last season.
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