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LONDON, Aug 28 (Reuters) - Chelsea striker Diego Costa has suffered a minor muscular injury in training but has not yet been ruled out of Saturday's league visit to Everton, sources at the Premier League club said on Thursday.
The full extent of the Spain forward's injury is not yet known, with some British media reports claiming he could face up to six weeks out.
Costa, who arrived at Stamford Bridge in a 32 million pounds ($53.04 million) move from Atletico Madrid, scored in Chelsea's league wins over Burnley and Leicester to start the season and any absence would be a big blow for Jose Mourinho's side.
Costa suffered a hamstring injury with Atletico at the end of the previous season that forced him to limp out of the Champions League final against Real Madrid after nine minutes and hampered his World Cup campaign with Spain.
($1 = 0.6033 British Pounds) (Reporting By Sam Holden; editing by Justin Palmer)