Chelsea striker Diego Costa is optimistic of a swift return to form for the Blues after a disappointing start to their Premier League and Champions League campaigns.

The Blues lost 2-1 at Jose Mourinho's former club Porto to slip to third place in Champions League Group G.

The Spain striker told espnfc.co.uk: "To come out of this we need to be all together, and for everyone to give a little more.

"We are not playing well, this is not a good moment, but we have players to get out of this easily."

"We had the game under control," Costa added.

"We knew it was going to be a physical game. We began well.

"Things changed when they scored, but we quickly equalised. In the second half the same thing happened - we were lacking concentration at key moments of the game."