Maybe he is getting used to having a healed hamstring again, after playing with a damaged one since last season. This sounds like nonsense, but really he looked less clumsy when 'injured' imo. Not worried about Costa at all, but if you want to worry about something then for me its his heading skills. Don't think he won an air duel today, despite him being one of the biggest and strongest guys in the PL. Oh and the number of yellow cards. Costa needs time, took the PL by storm but it is perfectly normal that he needs time.