That's not necessarily because of runs scored, although 328 at 41 is a fine return. It's more because of strike rate. Last night it was 227; across the tournament it's been 192, the best of any player to face more than 36 balls.
He's consistently freed up deliveries from which his teammates could consolidate an innings.
Last night, there were shades of Stephen Fleming's 134 not out from 132 balls to defeat South Africa at Johannesburg's Wanderers ground in the 2003 edition. The Duckworth-Lewis method played a role there, too.
McCullum went about his work seemingly oblivious to the pressure. The only time it showed was in the first over; he lost a shoe in desperation pirouetting back into his crease.
South African captain AB de Villiers needed to draw on a tactical gem. The solution? An over from leg-spinner Imran Tahir who, until yesterday, had taken 15 wickets at 18.86 and a run rate of 4.14 at the tournament.
Martin Guptill, on six from nine deliveries, was cautious. He played out a maiden over. Morkel came on from the south end. Whack.
McCullum advanced, got cramped, and clobbered to Steyn at mid-on. Tahir effectively bought Morkel a wicket.
But on a tide of national goodwill, McCullum delivered the catalyst for New Zealand's strong cup performances with four half-centuries.
He avenged what was a gap in his 13-year cricketing CV. Before this tournament he'd failed to make a World Cup half-century against a test-playing nation. His 2003-2011 World Cup record of 414 runs at 31.84 in 18 innings was deceptive. He had scored 308 against nations ranked outside the top eight. The other 106 came at 10.60, with a best of 36 not out against the West Indies in 2003.
His renaissance started with 65 from 49 balls against Sri Lanka, a local anaesthetic to ease public nerves; he honoured Wellington giving him the keys to the city with 77 off 25 balls against England; and he mashed 50 off 24 against Australia to set up the run chase for 152.
