South Africa, who lost the third Test by two wickets in Johannesburg yesterday, host New Zealand in a three-Test series starting on April 15.
''South Africa will still be very tough, you don't come here expecting anything less,'' Fleming told reporters after the New Zealand team's arrival today.
''They've been playing a level of cricket which makes you hard because Australia push you to the limit. South Africa had some good performances in isolation, but they needed a bit more,'' Fleming said.
Fleming said the form of paceman Makhaya Ntini, who took 19 wickets in the three Tests against Australia, had been the most impressive aspect of South Africa's game.
''The nature of their defeats was more interesting than the actual results, South Africa were by no means out of it.
Makhaya Ntini bowled very well, it's pretty clear that he's in good form,'' Fleming added.
New Zealand's own bowling spearhead, Shane Bond, is fully fit, while the Kiwis have paid extra attention to their top-order batting, expecting autumnal pitches in South Africa to be similar to home conditions.
''New Zealand playing conditions are often green seamers so there are not too many guys volunteering to bat up top. So the top-order batting has been a problem going back a long time to John Wright and Bruce Edgar,'' coach John Bracewell explained.
''But that's why we've chosen two specialist openers and a specialist number three for this tour, guys who want the job in Michael Papps, Jamie How and Peter Fulton."