The Spain international aggravated “minor muscular injuy” during first-team training this week, potentially ruling him out of the clash against top-five rivals Everton.
Initially, Costa, who moved to Chelsea in a £32m deal from Atletico Madrid earlier this summer, was reported to be facing six weeks on the sidelines following the setback.
However, Chelsea manager Mourinho revealed that the west London side have taken all possible steps to ensure that the 25-year-old is fit to face Roberto Martinez’s side this weekend.
“We are trying everything for him to play tomorrow. He didn’t train for the last two days. Today is the last day. He is a big doubt, let’s see. Everyone else is fit,” Mourinho told a news conference at Cobham on Friday.
Costa has made a bright start to life in the Premier League, scoring against Burnley and Leicester City.
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