Brendon McCullum has revealed that he was the driving force behind the recruitment of Kevin Pietersen as a specialist mentor to England’s white-ball teams and said the new arrival had specific orders to “look across the environment and challenge me”.

Pietersen spent his first day in the role monitoring training at the Utilita Bowl after delivering an address that had the players “buzzing”, according to McCullum, England’s white-ball coach.

McCullum revealed that Pietersen had “thought I was joking” when he made the initial approach to the 46-year-old. “Then he mentioned: ‘I’ve been quite critical of you guys in the past’,” McCullum said. “And I said: ‘I have no problem with that, mate’.”

“That’s the beauty of Kev coming in. He’s obviously got an incredible pedigree as a player and a lot of the guys grew up idolising Kev when he was in his pomp. He’s brought a ton of energy to the setup within the last 24 hours.”

With Marcus Trescothick returning to duty as assistant coach with a focus on batting, 48 hours after the conclusion of his time as interim coach of the Test team, Pietersen has been told not to focus on any single discipline. “I’ve mentioned to him that I don’t want him to be buried in one specific skill set,” McCullum said. “I want him to look across the environment and challenge me privately around ways we can improve things or can do differently.

“The way he looks at the game is quite different to a lot of people. Having someone that has a different take on things is no bad thing. You don’t know what you don’t know, but if someone can see something slightly different and point out something that can make you a better side, or a better coaching structure, I see that as no bad thing. Kev will do that and I’ve encouraged him to do that. From my point of view I see only up side.”

McCullum’s long-term replacement as red-ball head coach, Stephen Fleming, arrived on Monday in the country for a hectic and brief reintroduction to the domestic game, to include visits to several counties and to the national cricket performance centre at Loughborough, and meetings with the Test captain, Joe Root, as well as with the white-ball squad at their third T20 against Sri Lanka in Manchester – the final game of a series that starts on Tuesday in Southampton – before he returns to New Zealand next week.

“I think the team will really respond to his style and his approach,” McCullum said. “He’s a brilliant man, a brilliant tactician and a brilliant coach. I think he’s going to do a great job with that side.”

The two coaches are close friends, and inevitably discussed the offer before Fleming accepted his new job. “He said: ‘What do you think?’ I said: ‘I think you’d be brilliant. It’d be a great opportunity for you.’ I absolutely loved the job. They were the things I passed on to Flem. And I also thought for the group, for English cricket, he would be absolutely the right person to take this team forward.”

England will start the series against Sri Lanka without Phil Salt, Jacob Bethell and Sam Curran for fitness reasons, with Jofra Archer rested after his recent exertions with the Test side and with Brydon Carse absent for disciplinary reasons. In their absence Aneurin Donald, the Derbyshire batter who scored 31 off eight balls for the Lions against Sri Lanka last week, will make his debut as opener. “He’s a cricketer who has been on our radar for a long time,” McCullum said. “He’s got a game where he can go from ball one. He’s got raw power. Incredible amount of talent.”

Carse’s absence stems from a late-night fracas at a Derby bar last month, with McCullum saying this was an opportunity for the 31-year-old “to get his house in order”. In a change to the approach that has marked much of his time as England coach, the New Zealander said he was now unwilling to select players who cannot guarantee full commitment to a professional culture.

“I want us to be the fittest, strongest, most robust, dynamic one-day and T20 side in the world,” McCullum said. “That comes with hard work, commitment to training, but also the high octane style we want to play comes with responsibilities off the field to look after yourself. I know in the Test setup this has been talked about, and that’s completely consistent with what we expect from our players. If we want to play this style of cricket then we need to be living it daily, not just with our skills but our decisions off the field too.

“It’s the same message, not just to the guys within the squad at the moment but also to those who have got aspirations of representing England in white-ball cricket over the next 12 to 18 months. You need to make good decisions off the field that allow you to be the best version of yourself. I hope it’s crystal clear what is expected.

“There is a lot of talent around. If you’re not prepared to do that, there are other guys who will be given those opportunities.”