Chelsea manager Jose Mourinho says Diego Costa could miss the team's next four games with a left hamstring injury that has affected the Spain striker all season.

Costa, who has scored 19 league goals, limped off after a recurrence of the injury during Chelsea's 2-1 win over Stoke on Saturday.

Mourinho says ''we have eight matches to play - if he plays four, it's normal. If he plays three, it's a little bit below what I'm expecting.''

Chelsea leads the Premier League by seven points, with a game in hand, and plays Arsenal and Manchester United - its two closest challengers - in the team's next four games.

Chelsea plays west London rival Queens Park Rangers on Sunday.

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