Costa an injury doubt for Chelsea's trip to Everton

The Spain forward - who arrived at Chelsea from Atletico Madrid for a reported £32 million fee in July - has quickly settled to life in England.

Costa has scored in both of Chelsea's Premier League wins this term while his pre-season form was also encouraging.

But the 25-year-old could miss his side's visit to Goodison Park after a Chelsea spokesman confirmed to Perform that he was suffering from a "minor muscular injury".

Chelsea added that the situation would be closely monitored in the coming days.

The news will come as a blow to Jose Mourinho as he looks to guide Chelsea to a rare win at Everton.

The Merseyside club have won four of the last five league matches between the two sides at the venue. Ex-Chelsea striker Samuel Eto'o is in line for his Everton debut in Saturday's match.