In tandem with left arm spinner Mitchell Santner, a tourniquet was applied to the middle of the Pakistan innings. They still got to 262 for eight, but Williamson's spell of 10-0-32-2 was significant.
Bowling together Williamson and Santner took three for 61 from 18 overs.
It was just the second time the New Zealand skipper has bowled a full complement of 10 overs in an ODI.
The only other occasion was the Champions Trophy against Australia at Edgbaston in 2013, that day taking one for 56. It was a vastly different outcome yesterday.
Pakistan coach Mickey Arthur lamented his batsmen's failure to rotate the strike when the spinners were operating, recognising they had missed a trick.
"He bowled well, but not two for 32," Arthur said.
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"We need be able to rotate more and better against the spinners in the middle period."
Williamson's bowling career stalled in 2014 when he was suspended for having an illegal action.
He was cleared in December that year, but for a time after his return appeared reluctant to take the ball.
In the course of 25 tests since coming back to the crease after the ban, Williamson has bowled just 48 overs.
He has bowled in only three of New Zealand's last 14 ODIs, a form of the game in which his best figures are four for 22 off 7.2 overs against South Africa in Paarl in early 2013.
He has bowled in 11 of his 44 T20 internationals, taken six inexpensive wickets at a useful 7.9 economy rate.
All of which suggests Williamson shouldn't be shy of marking out his short runup in the future.