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. (For more sports news andupdates, followAhramOnlineSportson Twitter at@AO_Sportsand onFacebookatAhramOnlineSports.) http://english.ahram.org.eg/News/127363.aspx