It was the first time in 11 innings of 50 or more that Williamson had been in a losing New Zealand team.
The hosts made a spirited effort, highlighted by the seventh-wicket partnership of 74 from 57 balls between Ronchi and Vettori. Ronchi's sweet spot remains the size of a frying pan while Vettori is a nurdling guru.
"The middle to lower order was a positive with some good cameos to keep us in the game," Williamson said. "Sometimes it can be a bit tough to work ones on a drop-in pitch because the ball plugs a bit, so losing wickets can make it harder to rotate the strike.
"With the ball we weren't quite there but the wicket can change and we were slowish to adapt ..."
The visitors would have taken heart their maligned pace attack can survive sans Lasith Malinga. Nuwan Kulasekara, Shaminda Eranga and Dushmantha Chameera each took two wickets.
It justified stand-in captain Lahiru Thirimanne seeing a terracotta pitch and deciding to bat. The visitors reaffirmed why they're a difficult proposition even without Angelo Mathews (flu), Malinga (ankle injury) and Rangana Herath (family issue).
The top three of Thirimanne (30 off 41 balls), Tillakaratne Dilshan (81 off 98) and Sangakkara established partnerships of 71 and 104 for the first two wickets to set up the game.
Sangakkara overtook Sanath Jayasuriya as the highest ODI run scorer for Sri Lanka with 13,434 at 40.95 by innings' end. Dilshan and Thirimanne set a platform only broken in the 15th over. The key feature was the scant respect the trio held for Vettori as he went at more than a run a ball. It was the first time in 42 ODI bowling innings since September 2009 that Vettori had not completed his allotment of 10 overs in a full 50-over innings.
The New Zealanders earned a reprieve through Tim Southee and Anderson which was complemented by a crack fielding display, particularly from Guptill and Latham within the 30m circle.
Southee finished with two for 50 which included Dilshan and Mahela Jayawardene caught behind and Anderson earned three for 59 from nine to back up four for 52 in Dunedin.
Given the New Zealand's success over the summer, the crowd was disappointing. Acres of yellow seats were exposed despite a tongue-in-cheek letter, including NZC logo and a McCullum signature, which went viral on social media asking workers to be excused from their duties in the interests of patriotic duty.
New Zealand now have a selection conundrum for the two matches against Pakistan. Ronchi can expect a rest at some point, possibly tomorrow, to give Latham time with the gloves, and Anderson might have earned a refresher, but they must ask whether it is worth persevering with Guptill to coax him back into form.
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