Defending champions England, led by captain Jos Buttler, suffered six defeats in their first seven matches of the tournament and failed to qualify for the semi-finals, finishing in seventh place in the points table.

The early exit puts a sour note on an otherwise promising year for England, whose highly entertaining and aggressive "Bazball" approach in test matches has earned them plaudits.

"It's hard for me to be critical of Jos Buttler and Matthew Mott when I'm the one who, every single time the decision has been made for whether or not we focus on 50-over cricket, test cricket or T20, I've always chosen test cricket," Key told reporters on Sunday.

"I made the mistake of thinking that actually it will be all right when we get there and that's not been the case.

"You sort of made the assumption that, without playing lots of 50-over cricket, actually this is such a good team that will just slip into old habits and away we go."

Key added that white-ball coach Mott, who was appointed in May last year, needed to get the team "playing to their potential".

"We'll have some pretty honest conversations and say, 'right, what are you going to do to improve this?'? But he gets my full backing and an opportunity to try and turn it around," Key said of Mott.

"This actually should be the making of those two as a partnership," he said, referring to Mott and Buttler.

"If it isn't, it isn't, and you move on but we have to make sure some good comes out of what has been a very poor World Cup."

England next face the West Indies in a multi-format series featuring three ODIs from December 3rd-9th and five T20s from December 12th-21st.