Jose Mourinho and Diego Costa
Jose Mourinho's confidence in Diego Costa's fitness is slowly eroding Getty Images

Chelsea manager Jose Mourinho will not use Diego Costa's injury problems as an excuse for the club failing to retain their Premier League title should the Spaniard be dogged by the fitness issues that curtailed his maiden season in English football.

Costa spent three spells on the sidelines last term with a hamstring injury, but was still able to plunder 20 goals as the Blues claimed the title ahead of Manchester City and Arsenal.

Those fitness concerns have resurfaced with the new campaign having barely begun, with the 26-year-old having missed Chelsea's Community Shield defeat to Arsenal with another hamstring complaint suffered during pre-season.

And while Mourinho is unable to give any guarantees over Costa's fitness, the Chelsea boss is unwilling to use the absence of his main striker as justification for an inability to claim back-to-back league titles.

"No I can't say that [that Costa is no more susceptible to injury than anyone else]," he said at the official Premier League launch, according to BBC Sport.

"Last week he began the season injured, in the first game of this season, in spite of not [playing in] the Premier League, a Community Shield game he was not ready to play.

"I cannot reassure. The only thing I can reassure is that he is working well and hard and everybody around him is thinking about helping him.

"I don't like the word concern because I have other players. I don't like to cry or moan about players that don't play. But obviously in such a short squad like we have, then when somebody is missing I am not happy. But it won't be an excuse for me."

Following Filipe Luis' return to Atletico Madrid, Chelsea are close to signing a replacement in the form of Augsberg full-back Abdul Baba Rahman, according to the player's agent.

But Mourinho is coy over whether the club will complete a deal for a replacement defender and suggests that current squad players will be forced to play out of position to fill certain positions this term.

"I am always happy with what I have got," he added. "What I have is what I have. I like my people, I like players I like my squad I am happy to work with them.

"I am always confident. If we won't do business, we don't do business. We have good players. We have to get players to play in positions that are not their positions, to play in positions where we don't have cover and we have to be ready for that.

"We are working with players to play in other positions. I don't have a second left back but I have other players that we are working with to, in the future, able to play in that position in case we don't get cover."