They were dead at 27 for five in game one, and in Monday's second match, were all out for 117.
In a similar situation to the second test at Hamilton this month, when they appeared incapable of putting away the hook shot and knuckling down to a period of shoring up the ship as New Zealand went for a short-ball approach, Sri Lanka haven't shown an inclination to patience to steady things as wickets fell.
The fast bowlers have taken all but two of the 20 Sri Lankan wickets to have fallen - legspinner Ish Sodhi took one and there was a runout in the second game.
The combination of their work, rather than individual thought processes, is key, according to big left-armer McClenaghan - Milne with his extra speed, McClenaghan his bounce bowling, Henry and Bracewell more about accurate seam bowling.
"We all have different attributes and that's why we work so well as a group," he said yesterday.
"In the field you will see us talking to each other, just refreshing memories from scouting meetings, and giving ourselves a little more confidence that we are doing the right plan.
"We work together and the reason we're going so well is we are working as a collective not as individuals."
Henry took eight wickets in those games but he has returned to play Ford Trophy cricket for Canterbury, with Tim Southee back after a short break.
McClenaghan has had a rough year. Unwanted in the first choice XI for the World Cup, bar one disappointing outing against Bangladesh at Hamilton, he is determined to make the most of his chances, and with the carrot of the world T20 in India in March.
New Zealand insist Sri Lanka are a better ODI side than they've shown.
They won their last four matches before coming here, but there's been precious little resilience from the batsmen giving the bowlers little to work with.
It's inconceivable Sri Lanka can remain in their batting trough, although veteran opener Tillekaratne Dilshan will need to recover from a blow to the head suffered in the nets yesterday.
If New Zealand win today they'll extend their record of home ODI wins to 12.
NZ v Sri Lanka
Saxton Oval, Nelson, 11am today
New Zealand: (from) Brendon McCullum (c), Martin Guptill, Tom Latham, Kane Williamson, Ross Taylor, Henry Nicholls, Luke Ronchi, Mitchell Santner, Doug Bracewell, Ish Sodhi, Adam Milne, Mitchell McClenaghan, Tim Southee.
Sri Lanka: Angelo Mathews (c), Tillekaratne Dilshan, Danushka Gunathilaka, Lahiru Thirimanne, Dinesh Chandimal, Kithruwan Vithanage, Milinda Siriwardana, Chamara Kapugedera, Suranga Lakmal, Thisara Perera, Ajantha Mendis, Sachitha Senananaye, Dushmantha Chameera, Nuwan Kulasekara, Jeffrey Vandersay.
Fast bowling form
New Zealand seamers' numbers in the first two ODIs against Sri Lanka:
• Matt Henry 19.43-82-8 (average 10.2)
• Mitch McClenaghan 18-2-72-5 (14.4)
• Doug Bracewell 16-3-68-4 (17.0)
• Adam Milne 10-0-30-1 (one game only)