Vettori took a minor part in team training at Lord's Monday but the spinner, who injured his bowling arm at practice on the eve of New Zealand's seven-wicket win over Scotland, seems certain to be rested until the Super Eights.
Seamer Kyle Mills, who is returning from a back strain since arriving from South Africa, might get a place in the side.
New Zealand confirmed their progression from the group stage when a blazing batting performance atoned for some poor bowling against the unfancied Scots at the Oval Saturday night.
Vettori admitted the bowling effort against Scotland was "exceptionally poor".
"We didn't cope too well with the pressure of playing seven overs against a team we should beat," he said.
"Theoretically our game against South Africa is a dead rubber but Twenty20 is all about momentum."
Published 08 June 2009, 12:57 IST