2) Reliance on Costa
Making just 26 Premier League appearances last season, it’s clear that Diego Costa has a slightly worrying injury record – and in fairness, these things tend to get worse, not better, with age. The Spanish international is undoubtedly a world class striker, scoring 20 times in those 26 games to show how prolific he is at his best, but it may be unwise to rely on the 26-year-old as a permanent first choice in that role, particularly as backup forward Loic Remy has also found it hard to stay fit during his first season at Stamford Bridge.