Analysis - What has happened to Chelsea's Diego Costa?

By Tony Jimenez LONDON (Reuters) - Diego Costa has turned into a pale imitation of the player who took the Premier League by storm last year and Chelsea must get him firing on all cylinders again to have any hope of salvaging their wretched season. Chelsea fans, already mystified by their team's dramatic loss of form, are now wondering what has happened to Diego Costa. Eden Hazard, the 2014-15 Premier League Player of the Year, again showed the tricky, ball-playing skills that tormented defences