Taylor missed out, scoring only two, but is well on track to becoming New Zealand's most prolific century maker. He has 12 in tests, second equal with John Wright and behind only his mentor Martin Crowe (17). He also has 11 in ODIs, behind only Nathan Astle's 16 - Astle's combined total of 27 is also the standard setter.
With eight and three centuries in tests and ODIs respectively, Williamson has got a lot further to go but, at 24, has time on his side.
"Often we look back and say, 'how great was that player', but we might not celebrate them as much as we should while they're playing," McCullum said. "Kane and Ross are two guys we should be sitting back and enjoying watching them at work. They're not going to get runs every time but, geez, they're banging them out at the moment."
McCullum took over as captain when Taylor was jettisoned in controversial circumstances by coach Mike Hesson. If anything, his batting has grown more steely, more balanced, since losing the leadership.
"He's prolific in terms of his output," McCullum said. "He's grown as a team man in the last little while and, understandably, it took him some time to integrate back into the group and probably for a period of time his focus was more about his own game.
"What we see now is a guy who is pretty content in the environment. He's having a lot more impact in terms of leadership post-captaincy than what he did initially. It was a shit time. Everyone understands that. There were some wedges driven that didn't need to be."
The New Zealand captain, who is missing the one-dayers in the UAE to give him a breather ahead of a huge summer of cricket, even praised the way Taylor and Williamson celebrated centuries. Unlike other batsmen around the world, there are no histrionics, just a calm acknowledgement to team-mates and the crowd and then back to work. It's a 'non'-celebration McCullum expects to see a lot more of in the coming years.
Scoreboard
Scoreboard from the second ODI between Pakistan and New Zealand.
PAKISTAN
Hafeez c Latham b Henry
76
Shehzad c Ronchi b Henry
0
Khan c Taylor b McClenaghan
6
Shafiq b Henry
1
Sohail c Taylor b Anderson
33
ul Haq c Ronchi b Henry
47
Ahmed c Latham b McClenaghan
23
Afridi c Vettori b Milne
27
Riaz c Taylor b Milne
14
Tanvir lbw McClenaghan
14
Irfan not out
0
Extras (1lb 1nb 9w)
11
TOTAL (for 10 wkts, 48.3 overs)
252
FOW: 1, 11, 20, 97, 163, 172, 209, 231, 248, 252.
Bowling: M Henry 10-0-45-4 (3w),
M McClenaghan 9.3-0-56-3 (5w 1nb),
A Milne 10-0-53-2 (1w), D Vettori 10-0-48-0, A Devcich 2-0-14-0,
C Anderson 7-0-35-1.
NEW ZEALAND
Brownlie b Afridi
47
Devcich run out (Hafeez)
58
Williamson not out
70
Taylor c Ahmed b Sohail
2
Latham c Tanvir b Sohail
3
Anderson b Sohail
10
Ronchi c Tanvir b Afridi
36
Vettori not out
13
Extras (6lb 2nb 8w)
16
TOTAL (for 6 wkts, 46 overs)
255
FOW: 103, 129, 138, 148, 167, 225.
Bowling: S Tanvir 6-0-30-0 (2w), M Irfan 10-0-50-0 (2w 2nb), W Riaz 9-0-58-0 (2w), S Afridi 10-0-47-2 (1w), H Sohail 9-0-48-3 (1w), A Shehzad 1-0-7-0, A Shafiq 1-0-9-0.
International records
Kane Williamson
Tests
Played: 37
Runs: 2638
High score: 192
Average: 41.21
100s: 8
One-dayers
Played: 56
Runs: 1779
High score: 145 not out
Average: 40.43
100s: 3
Ross Taylor
Tests
Played: 60
Runs: 4550
High score: 217 not out
Average: 45.95
100s: 12
One-dayers
Played: 139
Runs: 4435
High score: 131 not out
Average: 40.68
100s: 11