Like McCaw, Williamson is a guaranteed selection. Such a luxury should not be taken for granted, and Williamson's passive nature should not be misunderstood. It camouflages a steel core. Anyone who has watched him practise would attest to his discipline.
Much has been made of the successful team culture under McCullum and coach Mike Hesson over the past two-and-a-half years, but it has been dependent on commitment. Williamson's work ethic has been exemplary, as has his devotion to a team ethos.
If he brings those components to the captaincy, and his team-mates - who already respect him as a player and person - feel compelled to follow, New Zealand should extend their rosy era.
Williamson is more of an introvert to McCullum's extrovert, and it will take years to accumulate the incumbent's chutzpah, but the heir has a prime opportunity to set a benchmark across the upcoming six ODIs and three T20Is in Zimbabwe and South Africa.
New Zealand have won four and lost five in nine previous ODIs with Williamson in charge. Those results include a 3-2 series victory away against Pakistan in December, when Williamson top-scored with 97 in the decider (New Zealand won by 68 runs). He scored 346 runs at an average of 86.50 and strike rate of 90 across the series.
He looked flustered on occasion juggling the bowling changes, field settings and over rates, but that's part of the territory adjusting to any new job, especially in tight matches.
Williamson has the added conundrum of being without bowling spearheads Tim Southee and Trent Boult, and the all-round dynamism of Corey Anderson and Mitchell Santner meaning it will be a rigorous test.
5 questions to ponder
1. How does Jimmy Neesham transition back as the key all-rounder in Corey Anderson's absence?
2. Can Ish Sodhi, with his ability to spin the ball both ways and deliver useful batting cameos, threaten the primacy of Nathan McCullum?
3. Can Tom Latham establish himself as the logical replacement to assume opening duties once Brendon McCullum retires?
4. How has Adam Milne's body recovered after his heel injury?
5. How will Milne, Matt Henry, Mitchell McClenaghan, Doug Bracewell and Ben Wheeler cope with the pace bowling responsibilities sans Trent Boult
and Tim Southee?