New Zealand made a smashing start to their World Cup campaign as paceman Matt Henry took three wickets in a 10-wicket drubbing of Sri Lanka.
Henry and Ferguson shared three wickets to bowl out Sri Lanka for 136.
Martin Guptill and Colin Munro smashed half-centuries to chase down the total in 16.1 overs.
Henry took the responsibility in the absence of Tim Southee, who had to sit out due to a calf injury.
He struck on the second delivery of the game to send Lahiru Thirimanne back to the dugout.
Thirimanne was initially ruled not out by the on-field umpire, but the Kiwis successfully reviewed the leg-before call in their favour after replays suggested the ball pitched in line and would have gone on to hit the stumps.
Skipper Karunaratne then constructed a 42-run partnership for the second wicket with Kusal Perera.
But Williamson persisted with Henry on for the bowler's fifth over and the decision paid off as he got rid of Perera and Kusal Mendis on consecutive deliveries.
However, skipper Dimuth Karunaratne fought on to register his third ODI fifty in 81 balls before he was short of partners.
Karunaratne's unbeaten 52 made him only the second opener in World Cup history to carry his bat.
The feat had previously been achieved by the West Indies' Ridley Jacobs, who made an unbeaten 49 against Australia in 1999.
Colin de Grandhomme, James Neesham, Trent Boult and Mitchell Santner took one wicket each.
New Zealand will now face Bangladesh on June 5, while Sri Lanka play Afghanistan on June 4.