Chelsea Premier League 2015-16 preview: Diego Costa fitness holds key to successful title defence

Last season

Premier League: 1st

FA Cup: Fourth Round

League Cup: Winners

Top scorer: Diego Costa (21)

Summer's work

The normally active Blues have been among the most reserved clubs in the Premier League in the transfer market. Asmir Begovic has replaced Petr Cech and Radamel Falcao has come in for Didier Drogba. Filipe Luis has returned to Atletico Madrid after just 12 months in English football, with the signing of a left-back stand-in imminent. At the time of writing, 19 players have been loaned out by the Premier League champions.

Manager - Jose Mourinho

After a docile approach in his first two campaigns back in England, psychological warfare has taken over in pre-season, perhaps because the Portuguese boss is in the knowledge that the challenge facing his team this season is among the sternest of his career.

The Chelsea boss has already taken aim at Arsenal while his envy of Manchester City's spending is well known. Claims his squad is not big enough, and resources in defence are threadbare are already evident; a good sign he fears his grip on English football is loosening.

Key player – Diego Costa

Player of the year Eden Hazard may be the greatest asset in the Chelsea squad but it is accepted that the success of the club's title chances rest on the form, and fitness, of Costa.

The Spaniard was constantly in the headlines last term, if not for goals then for his temperament, which was tested throughout the campaign.

Costa starts the 2015-16 as he spent three different parts of last term, injured, and Mourinho has been unable to make any guarantees over his fitness.

Diego Costa begins the season injured and with questions over his ability to survive the Premier League Getty Images

Expectations

Without having to be at their best for the last four months of the campaign, the eight points Chelsea finish ahead in the title race flattered their rivals.

Though defensive options are few and far between, the attacking resources Chelsea have are among the best in Europe and in Hazard they have the overwhelming player of the year from last season.

Anything less than a comfortable defence of their title, and progress in the Champions League, would be a surprise for the Stamford Bridge faithful.