After losing the first Test in Perth in two days, England also decided against sending their first XI players to Canberra to play in a pink-ball practice match before the day-night second Test and instead arranged extra sessions in the nets at the Gabba.
McCullum suggested less time in training would have been more beneficial.
“The five intense training days leading into Brisbane when we knew it was going to be hot,” he said. “A few things you look at retrospectively.
“Your job as a coach is to try get performance on the field. I was confident we had it right but obviously we didn’t.”
In assessing the series, McCullum also said England’s bowlers had been unable to be “accurate and precise” with the ball and their batters failed to “score the volume of runs”. He also praised Australia as “as precise as a team as I have seen in the last few years”.
He said at times England were “so determined” and had “such high expectations” for the series that it “almost constrained us”.
A relaxed environment has been a hallmark of the McCullum-Stokes regime, as has an aggressive attitude with bat and ball.
“The last two days [in Adelaide] have been our best cricket and that is because we have just played,” he said.
“When you’re put under immense pressure, your decision making can become a little blurred at times and you don’t know whether to stick or twist.
“That’s probably the disappointing aspect because I did think we were rock hard in our belief of the style we were going to play when we were down here, knowing we were going to be challenged.
“But I do think we got a little bit stuck and, again, I’ll put my hand up as coach and say there should have been that absolute clarity of ‘whatever happens in this series, this is how we need to play’ because that is going to give us our best chance.”
