Diego Costa
Costa is doubt for the Premier League opener.Getty Images

Chelsea manager Jose Mourinho has revealed he was forced to leave Diego Costa out of his squad for Sunday's Community Shield defeat to Arsenal after the striker suffered an injury setback on Saturday.

The Portuguese boss had said on Friday 31 July that Costa was ready to play against the Gunners despite suffering a hamstring problem in the pre-season game against Barcelona.

But the Spain international was finally excluded from the match day squad after a fresh problem during Saturday's training session - with Loic Remy starting the game and Radamel Falcao coming on after half-time.

Mourinho has explained Costa's omission while also revealing he is still doubt for the Premier League opener against Swansea on Saturday 8 August.

"Two days ago he was ready to play. When I told you two days ago he was ready to play he was ready to play. He trained normally on Friday and yesterday at the end of the training session he said he was not feeling good," Mourinho said in the press conference after the 1-0 defeat against Arsenal.

"But Falcao will have had a bit more football, he will play against Fiorentina from the start. We have Remy too, so if we don't have Diego I am happy with the strikers I have."

The Portuguese boss went on to congratulate Arsenal for the victory at Wembley but suggested Arsene Wenger abandoned his attacking philosophy to secure his first victory against the Portuguese in 14 games.

"For me it depends on the perspective. Normally you [the media] like to say a team that is defensive and defends very well doesn't deserve to win," the boss said.

"But I also have my opinion, different from your opinion. My opinion is the team that defends very well, that leaves their philosophy in the dressing room, changes their attitude, plays all the second half with nine players in front of the box, doesn't concede and scores one goal, from that perspective they deserve to win."

"This is football. This is very good tactical organisation. Congratulations to them."