Costa's fitness
Diego Costa’s debut season with the Blues was marred by the recurring hamstring injury that forced him to the sidelines on several occasions. The 26-year-old still hasn’t completely recovered from the problem. However, manager Jose Mourinho insists Costa is fit enough to withstand another gruelling campaign.

Cech's impact
Petr Cech’s signing has gifted Arsenal boss Arsene Wenger a solution to a problem that had plagued his team for several years. After watching ’keepers commit costly errors, Arsenal finally have a world-class keeper, and a dressing room leader, to bolster the confidence of a sometimes shaky defence.