"No one's sure when it happened but it's a chance to rehab his shoulder so it doesn't inconvenience him later in the year," coach Mike Hesson said yesterday.
"He played the second test, had some medication and no issues. We don't want him on medication for a long time."
No Williamson is a chance to reshuffle a batting order which should not be locked in for the World Cup just yet in any case.
Familiarity in roles is a good thing, but there's no harm to tinkering for at least another few games - albeit underpinned by the desire to treat these games as serious ODIs in their own right, not a jolly pre-Cup potter about.
Ross Taylor returns after having the three-wicket win in Christchurch on Sunday off. Seamer Tim Southee is expected to miss Hamilton and return for Eden Park on Saturday, while fellow bowler Kyle Mills will miss the next two games as he recovers from a groin injury.
Hesson didn't identify who will bat at No 3 yesterday, but he's got options. Taylor could move up a spot from his regular No 4; Latham might be worth having a run there.
He is being touted as being in a battle for the No 5 spot with Elliott. Latham spent 30 balls over 15 before being stumped on Sunday; Elliott laboured six balls for one. Hesson is not about to dump on the recalled Wellington player.
"He'll be far better for the experience. He's relatively philosophical. That's the beauty of experience.
"You can wash it away as not a great day at the office but we know he's a fine player," Hesson said of 35-year-old Elliott.
There won't be any hasty decisions on the pair.
"We won't be jumping to any conclusions. Both Grant and Tom will get plenty of opportunities."
Hesson gave New Zealand a significant pass mark for the opening ODI - "90 per cent excellent, 10 per cent untidy" - although the batsmen, apart from Brendon McCullum and Corey Anderson with their half centuries, need to brush up. Martin Guptill, Williamson, Latham and Elliott mustered 31 in all from 61 balls.
Offspinner Sachithra Senanayake caused problems in his third match back after a five-month ban to straighten his bowling arm. In three ODIs since his layoff, he's taken seven wickets at 15 apiece.
"He's a quality bowler and creates different challenges. As a batting unit we'll be better off for it," Hesson said.
Anderson scored 13 runs off 21 Senanayake deliveries on his way to a match-deciding 81 off 96 balls at Hagley Oval.
"He's a pretty regulation spin bowler. He has the one that comes out the front [of the hand] and swings a little but other than that you play him as a conventional offspinner."
Look for that at Seddon Park on Thursday.
