When England built their World Cup-winning 50-over team in the years leading up to 2019, white-ball cricket – and particularly 50-over cricket – was a priority.
A year on from the Ashes away series, seen by many as the highlight of the red-ball side's Bazball journey under McCullum and Ben Stokes, that is no longer the case.
One of McCullum's biggest challenges will therefore be getting his best XI onto the pitch in white-ball games – or even getting enough time with the players at his disposal to assess what his best XI actually is.
It should come as no surprise that England's white-ball results have declined at the same time as the country has been without its Test stars so regularly.
Joe Root, for example, has played just 28 ODIs in over five years since the 2019 World Cup. In the 18 months leading up to this tournament he played 35 times.
The Yorkshireman was one of several Test players absent from the Caribbean tour, alongside Harry Brook, Ben Duckett, Jamie Smith and Gus Atkinson, to name a few.
Then there's Ben Stokes: hero in England's last two World Cup finals.
He has not played a limited-overs game for England since the 2023 World Cup but has said he will return to the squad at McCullum's request.
At 33, he remains a match-winner with the bat at least – his last ODI wicket came in March 2021 – but considering it's been less than a year since his knee operation and he plays an important role leading the Test side, that's true for England Would you like to increase his workload?
“The captain and I haven't spoken, but I assume he's fully involved. He seems like that kind of guy,” McCullum said in September, perhaps hinting at the answer to that question.
“He loves big moments and big stages.”
Given that Duckett, Root, Brook, Stokes and Smith could well form five of England's top seven players in 50-over cricket, McCullum's job could be to balance his Test players' rest periods with playing time in order to roll It is almost impossible to establish within your team with white balls.
A slightly more forgiving schedule in 2025 compared to previous years will help, but it is still likely that concessions will have to be made when it comes to three-format players like Brook or possibly Jofra Archer.