England coach Brendon Mccullum has conceded that the team's much-hyped 'Bazball' approach needs some "adjustment" after India exposed its frailties and forced the visitors to become "timid" during the recently-concluded Test series here.

England started with a thrilling win in Hyderabad but things went downhill for the visitors from there as India bounced back in stunning manner to take the five match rubber 4-1.

"Sometimes, you can get away with things. But when you're exposed the way we have been in the back end of this series in particular, it does require some pretty deep thinking and some adjustment to make sure we're staying true to what we believe in," McCullum told the travelling British media on Sunday.

"If anything, we got more timid as the series went on, and that was because of the pressure that was applied to us by the Indian line-up, not just with the ball. With the bat, they put us under a tremendous amount of pressure, too," he added.

Indian youngsters played a prominent role in the series win. In the absence of key players like Virat Kohli, Mohammed Shami and KL Rahul, the likes of Yashasvi Jaiswal, Dhruv Jurel, and Sarfaraz Khan led the charge.

The series loss was England's first in the 'Bazball' era.

Ben Stokes and Co. are now winless in three series and critics have panned the one-dimensional philosophy of aggression.

"There are some things where you can get a little bit of luck on your side and you paper over a couple of the cracks. When you are exposed in the way we have been here, you know that you have to get better in some areas," McCullum said.

"The next couple of months will be us working out that and making sure when we come to the summer we are a more refined version of what we are at the minute." England were guilty of squandering strong chances in the second, third and fourth Tests while their batters displayed poor judgement, giving away their wickets.

"Whether that affected our approach a little bit and put some doubt in our minds that wasn't there early in the series, I'm not really sure why at this point in time.

"They probably outplayed us at the style of cricket that we want to play and made us start to retreat a little bit. So that's something that we will have to change," McCullum said.