McCullum admits England have been 'nowhere near' their best

The tourists were crushed in the first two Ashes Tests in Perth and Brisbane by eight wickets and only a win at Adelaide Oval this week will be enough to keep the five-match series alive.

McCullum confirmed they would stick with the same top seven, keeping under-fire Ollie Pope at number three rather than bring in Jacob Bethell.

"Knee-jerk reactions and chopping and changing settled batting line-ups is not really our way," he said.

"We know we haven't got enough runs so far in the series. But for us to go on and win the series it's not about throwing out what's been successful for us over the past few years."

England's lack of fight and questionable preparations have drawn scrutiny, while McCullum's claim that they "trained too much" prior to Brisbane was met with disbelief by former greats.

A decision for the team to lounge on the beach in tourist playground Noosa this week before heading to Adelaide was also panned.

But McCullum was unfazed, dismissing talk that his job could be threatened by another defeat.

"I don't know, but it doesn't really bother me, to be honest," he said.

"I mean professional sport, it's not easy, right? You do the job to the best of your ability. You have conviction in what you're doing, and whatever happens, happens."

McCullum admitted England must improve to keep the series alive, but suggested they would not change their gung-ho approach.

"We knew when we came here that we had to win three Tests to win the series, and the fact we're 2-0 down has made it harder on ourselves, but it doesn't stop the belief that you have within the dressing room," he said.

"I don't think we've been anywhere near our best so far in these last two Tests ... but what's been has been. Now, it's focusing on the one that's coming.

"I firmly believe that if we play our best cricket, we're a massive chance in this Test match. We do that, and the narrative changes in the series," he added.

McCullum defended the decision to take a beach break rather than train after two heavy defeats.

"Noosa for us was excellent. It was planned, obviously a year ago," he said, adding that it was about spending "time away from the heat of the battle".

"And I think now the freshness which we come into this Test match with will hopefully pay off.

"There's no guarantees, but that's the plan, and I think the boys are excited to get back to training and look forward to the next few days."