Williamson's progress through this tournament will be every bit as vital as McCullum's fireworks. Photo / PHOTOSPORT
There's a story which encapsulates the reason Kane Williamson is shouldering his way higher into the ranks of the world's best batsmen.
After last week's 119-run victory over Pakistan, Williamson could have joined the rest of the Black Caps in celebrating, particularly after his 88-ball 112. Nope. Instead of heading for a massage, ice bath or, gasp, a beer, he was back in the nets after the match.
Apparently he'd scored his runs too fast. Williamson not only prizes his wicket, he hankers after time in the middle. The story goes he was looking for 140 or 150 balls during his innings. That didn't happen, so it was back to the nets to make up the difference - and then some.
That not only augurs well for Williamson but for the Black Caps in the upcoming World Cup. His world-class emergence has given the team a presence at No3 that allows Brendon McCullum to play his master-blaster game at the top of the innings. When it comes off, New Zealand are highly dangerous.
Williamson's form in the 11 ODI matches the team have played since December has stamped him as our key player, even more so than the ebullient McCullum. Martin Crowe has already labelled Williamson's current run as "the dawn of probably our greatest ever batsman". In those 11 matches, Williamson scored three centuries, two 97s, 70 not out, 54 and 46 - 753 runs at an average of 75.3, remarkable even if the opposition was either Sri Lanka or Pakistan.
In comparison, McCullum, who has just had perhaps the most stellar year of any New Zealand batsman, has scored 331 runs (one century, amassing 331 runs at an average of 30.09).
It's not just Williamson's acclaimed technique which gives him (and us) confidence, it's that mental strength and hunger for success that took him back to the nets post-Pakistan.
It's why, when I look at him, I sometimes see Glenn Turner. Like Turner, Williamson has built his game around a defensive technique. Like Turner, he has morphed from a conservative player, carefully farming runs, into a free-scoring batsman. His 112 against Pakistan was his fastest ODI ton if you overlook the 69-ball century against Zimbabwe in 2011.
Turner's defence-oriented style was more exaggerated than Williamson's (at first Turner was sledged by nasty fasties who made fun of his slow scoring). As time in the middle passed, Turner grew his attacking skills; the snail became the greyhound, the introvert became the extrovert, sipping a gin and tonic in quiet celebration in the middle of the pitch when he passed that mark no other New Zealander has - 100 100s in first-class cricket.
Guess who stands at the top of New Zealand's ODI averages (1500 runs or more)? That'd be Turner, with an average of 47.00. Second? Williamson (now at 46.26). Ross Taylor (just under 42) is the only other Kiwi to average more than 40 in ODIs - familiar names like Crowe (38.55), Guptill (37.11), Andrew Jones (35.69), Nathan Astle (34.92), Jesse Ryder (33.21), Scott Styris (32.48) and Stephen Fleming (32.41) fill out the top 10 which does not include BB McCullum (30.27).
Williamson looked like Turner when he first started playing ODIs - and began his one-day career with 0, 0, did not bat and 13 before his first century against Bangladesh in 2010. He was essentially defensive, parsimoniously guarding his wicket, picking up ones and twos and holding up an end. He looked like Tom Latham does now - a test player picking his way carefully through the thorns of short-form cricket, someone who hasn't quite discarded the L-plates.
Williamson has now shown his range of skills - not just that almost-impeccable defence. He uses his feet better than any other Kiwi batsman, has the rarely-seen (on New Zealand pitches) ability to play off the back foot and has the mark of the greats - he sees the ball early and can steer it through gaps. Not only is he staying in the middle, he is scoring runs at pace.
Turner, interviewed in 2011, said: "He seems to have patience. What sets batsmen apart is making good decisions at the crease and he is hungry for success so keeps doing it. Where others fall down is they might make good decisions for a while then they almost give it away. You could tell with Kane that he wasn't keen to give it away. He was miserable with his wicket."
That could have been someone talking about Turner.
There's a caveat to all this, of course. He's only 24, there's the massive pressure of a home World Cup and this is the Black Caps - a team with a bewildering ability to dash our hopes on the rocks of expectation.
Williamson's record still has a few holes. He has made runs against South Africa (his highest ODI score of 145 not out) but has played England only six times in his 65 matches (average 31).
His only ODI outing against Australia came in a washed-out Champions Trophy game in Birmingham in 2011 (18 not out). That will make the match against Australia at Eden Park of intense interest - the Aussies will have plans for him.
From a Kiwi point of view, Williamson's progress through this tournament will be every bit as vital as McCullum's fireworks. It will be fascinating.