Head coach Brendon McCullum said England are unlikely to make changes to their batting line-up for the crucial third Ashes Test in Adelaide, which begins on Wednesday. England, 2-0 down after the first two Tests, must beat Australia at the Adelaide Oval to keep their hopes of regaining the Ashes alive.

Number three Ollie Pope and wicketkeeper Jamie Smith may have been candidates to be left out if England had considered making changes. But asked if he anticipated fielding the usual top seven, McCullum said: "I would have thought so. We've been in positions where we have made some mistakes, and that can happen at times. But for us to go on and win this series, it's not about throwing out what has been successful for us over the last few years. It's about having more conviction.

"Knee-jerk reactions and chopping and changing settled batting line-ups is not really our way." It is unusual for McCullum to address the media before a Test, and he explained his appearance on Sunday was because "we know where we are in the series".

In wide-ranging comments, McCullum:

• left the door open for spinner Shoaib Bashir and seamer Josh Tongue to play in Adelaide
• said any speculation that his job would be on the line if England lose this week "does not really bother me"
• explained his previous comments about England being "overprepared" for their second-Test defeat in Brisbane
• rejected any suggestion his team go about things in a "casual manner".

With changes to the top seven now seemingly off the table, England could opt to refresh their bowling line-up. Conditions in Adelaide, including the high temperatures forecast when the Test begins on Wednesday (23:30 GMT on Tuesday), could necessitate the inclusion of specialist spinner Bashir. All-rounder Will Jacks was chosen ahead of Bashir in Brisbane, though captain Ben Stokes insisted Bashir remains England's first-choice spinner. The 22-year-old was earmarked for this trip more than a year ago, but has not played a Test since July because of a broken finger and has figures of 2-266 from his two tour games in Australia.

Tongue would be the most likely candidate to come in if England want a new paceman, with Gus Atkinson possibly making way. "We need to have a look at the conditions," McCullum told BBC Sport. "We have a squad of 16 here, which in a five-Test series, we know we will have to call upon the majority if not all of those. We will work out what we think is the best option to be successful in these conditions."

Heavy defeats on Ashes tours have often brought changes to England regimes. This series was billed as a huge opportunity for England to win back the urn, yet the tourists are at risk of being out of the series at the earliest possible opportunity. Though McCullum and Stokes are contracted to England until the end of the next home Ashes in 2027, their positions - along with that of director of cricket Rob Key - will come in for intense scrutiny if England are beaten in Adelaide.

Asked if a loss would put his job under pressure, McCullum said: "I don't know, but it doesn't really bother me, to be honest. I certainly don't coach to protect the job. I coach to get the best out of people and that's the same with the skipper. We both go about that in our same way with the same level of conviction and that won't be changing this week just because the prize is at its highest. I firmly believe that if we play our best cricket, we are a massive chance in this Test match. If we do that, then the narrative changes and the series momentum changes."

In the run-up to the second Test, England chose not to send players from the first Test to join a day-night England Lions game against a Prime Minister's XI in Canberra. The tourists instead opted for five days of training in Brisbane which, in the aftermath of the Gabba defeat, McCullum claimed left them "overprepared". On Sunday, the former New Zealand captain said he stood by his comments, but also explained he made them to draw attention away from the players.

"There's things that you say and things that you do - in the job you're in, sometimes it's better for the scrutiny to be on yourself," said McCullum. "There is no perfect preparation. If there was and you could hit 4,000 balls to guarantee an average of 90, or bowl however many balls to guarantee 10 wickets, then we'll do it - don't worry. But that doesn't exist. Five intense days leading up to a Test match is not the best way to prepare. We'll be working out these next three days to make sure we get ourselves in the right frame of mind and skill level to be able to perform."

England returned to training on Sunday following a break in the Queensland resort town of Noosa. Their approach has often attracted criticism, in particular their off-field activities during this tour. On Sunday they began their training session with intense fielding drills, which have been uncommon for England under Stokes and McCullum.

"I do feel like there's a feeling that we go about our work in a very casual manner, but it couldn't be further from the truth," added McCullum. "The level of intensity with which we try to operate with and the hard edge we try to bring to the team, is all encompassing. It's how we try to live our lives and set about this cricket team."