Captain Stuart Broad does not believe his team have any mental scars from their hapless performance against spin in Sunday's record 90-run defeat against India in Colombo.
And Test captain Cook agreed as he said: "The important thing is we're through the group, so there's a clean slate. They had a bad game but that can happen to anybody and I'm sure the lads will be working hard to put that right."
He added: "You've got to have the balance of responsibility and skill to play a big shot - that's the skill in Twenty20, staying calm when a lot of things are happening very quickly.
"I've got no worries. There's a huge amount of talent in that side and Stuart and the lads will prove what good players they are."
Cook was unable to provide any developments in the Kevin Pietersen situation.
Pietersen, unavailable for the defence of the ICC World Twenty20 because of his differences with the England and Wales Cricket Board, is instead fulfilling a lucrative contract as television pundit for the tournament from a Colombo studio.
Cook added on Sky Sports News: "We know the qualities he brings as a batsman but clearly issues have to be resolved before he comes back in to the side. Hopefully they can (be)."