Diego Costa
Diego Costa is yet to make a significant impact for the Spanish national team Getty Images

Spain boss Vicente del Bosque has admitted disappointment with the performances of Diego Costa at a national level, but has backed the Chelsea hitman to approach his best before the European Championship in 2016. The 26-year-old striker has hit the net repeatedly in recent seasons, both at Atletico Madrid and then with Jose Mourinho's outfit, but has failed to reproduce that form for Spain.

Costa was expected to fill the gap left by the ageing David Villa and Fernando Torres in the national team during the 2014 World Cup, having opted to represent Spain despite being born and raised in Brazil. He failed to make an impact during the tournament, scoring no goals and being made a scapegoat for the piteous Spanish performance.

Spanish pundits have long felt his aggressive style does not fit with La Roja's more delicate passing game. Others have called his commitment to the country into doubt, with the player ruling himself out of games against Belarus and Germany in November 2014 citing injury – even though he had played a full game for Chelsea just days before.

Costa has given ammo to his detractors, scoring just once in seven appearances for Spain and missing call-ups in March and June due to poor form and recurrent hamstring issues. Del Bosque explained recently that he had decided to give Costa a new chance, including him in the squad for the coming European Championship qualifiers against Slovakia on 5 September and Macedonia three days later.

Asked during an interview with Cadena Cope about Costa's return to the national team, Del Bosque said: "We count on his willingness and his interest to play for Spain. The rest of the team are going to try to try to make the life better for him here. We can't be very happy with what he has done for us but I have seen playing well for Chelsea in recent games and that why he has returned to the team."

Costa has scored just one goal in Chelsea's first four Premier League games, also missing the Community Shield loss to Arsenal with a hamstring problem.