The 35-year-old Buttler has looked out of sorts in the five matches at teh global tournament, only managing a total of 60 runs with a highest score of 26, which in the opener against Nepal.
The wicketkeeper-batter looked all at sea against spin as he struggled for 7 in 14 balls in England's 51-run victory against Sri Lanka in Pallekele on Sunday.
Brook, however, remains in no doubt whatsoever that the former skipper will come good as his team chase a place in the semifinals.
"He's a powerhouse of world cricket," Brook said about Buttler at the post-match presentation. "He has been for many years.
"He's arguably the best white-ball player to have ever played the game, and he's just lacking a little bit of confidence at the minute.
"But I'd rather him start the competition like this and finish with a flourish. So I'm looking forward and I'm really excited to see how he goes the next couple of games.
"Jos hasn't fired yet. But when he does fire, and he gets on a very good wicket, he's going to get a hundred and blitz the team away. Same with Salty as well.
"He's got 60 today, but it's not the flourishing Salty that we know. Once we can figure that powerplay out, and get on top of them with the bat, then we're going to be a very hard team to beat."
England next face Pakistan in Pallekele on Tuesday where a victory would them in strong contention for spot in the last four.
England's T20 World Cup campaign got a much-needed boost as Harry Brook's side defeated co-hosts Sri Lanka by 51 runs in their opening Super 8s match, maintaining their perfect record against the island nation in recent encounters.
England captain Harry Brook is hoping the rain stays away but insists his side will adapt as they prepare for their opening Super Eights clash against Sri Lanka in the T20 World Cup.
Jos Buttler admits being frustrated about his lack of runs in the group stages of the T20 World Cup, but is keen to contribute for England in the Super Eights.
England were made to sweat for large parts but eventually showed their metal before beating Italy by 24 runs to book their place in the next round of the T20 World Cup.
