The 25-year-old striker has scored nine goals in seven Premier League games since moving to Chelsea in a big-money move from Spanish champions Atletico Madrid in the close-season.
However, Costa's season has been blighted somewhat by a persistent hamstring injury, and that issue, combined with a virus, means he has not featured for Chelsea since playing in Spain's Euro 2016 qualifiers against Slovakia and Luxembourg earlier this month.
Chelsea manager Jose Mourinho laid the blame for Costa's current absence on his involvement with Vicente del Bosque's side, but Spain team doctor Juan Jose Garcia Cota has refuted those claims.
"This time he [Costa] didn't say anything about the hamstring," Cota told IBTimes UK. "When Costa arrived to the international team he said to us he had a minor hassle in the groin but that it was nothing important.
"He probably had played with it before for Chelsea and he didn't complain any more about it during the international duty.
"He was treated by the physios [like every other player] and didn't have any limitations when doing exercises.
"I wouldn't even say it was an injury or a problem. It was a very minor hassle that is very common in every professional footballer.
"He didn't even ask for treatment and didn't require a scan or anything similar."
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