Where to now for Morris and Olivier?

South Africa went into this New Zealand Test series with six seamers in their squad. Less than halfway through, they released one, when Chris Morris was sent home on the second day of the Wellington Test. Two-thirds of the way in and they've let another go - Duanne Olivier returned to South Africa instead of traveling on to Hamilton.

And now there are four.

Morne Morkel, Vernon Philander, Kagiso Rabada and Wayne Parnell remain, but that does not mean South Africa have established an exact order of preference for their quicks. It means the infant Test careers of Morris and Olivier, who have three Test caps between them, are not in danger if the pair are willing to be patient despite being dispensed with.

Olivier may consider himself the unluckier of the two. Aside from an impressive debut at the Wanderers against Sri Lanka in January, he topped the first-class wicket-takers list with 52 scalps. For that reason, Olivier was thought to be in direct competition with Morkel for the third seamer's spot at Basin Reserve but it went to Morkel despite a year-long, injury-enforced absence from the game.

At the time, it was a gamble but South Africa took it after closely monitoring Morkel's recovery and because captain Faf du Plessis is a firm believer in Test cricket being the arena for the experienced. He can't be blamed for feeling that way. Du Plessis was witness to South Africa's sobering summer in 2015-16, when they were without Philander and Dale Steyn, lost five of eight Tests - three in India and two at home against England - and fell from No.1. Morris was among the players they tried without much success that summer.

Rabada provided some joy and has since then established himself in the South African side to such an extent that it is difficult to imagine a Test XI without him, which also means there is one less place for the likes of Morris and Olivier.

However, workload is a constant concern for Rabada, especially as he is only 21. There was some discussion about resting him, with talk centering on the New Year's Test against Sri Lanka after he appeared down on pace in the opener on Boxing Day or the upcoming Hamilton match where a spin-friendly surface may negate the need for three quicks. But even if South Africa are considering that, they have not showed their hand early by sending Rabada home and with New Zealand scrambling for morale, they shouldn't. The longer the hosts think they will have to front up to Rabada, the better for South Africa.

Realistically though - and looking beyond this series - Rabada may not be able to play all the time. South Africa will want to save him for the important stuff and therein lies opportunity for someone else.

Philander and Morkel are at their peak but they are also in their 30s and may only have a few years left. While they are fit, they are first-choice but that doesn't mean the door is closed to anyone else. Not even to Parnell, who has not played Tests since January. He was seen bowling on the practice pitch before the Wellington Test and the signs pointed to his inclusion ahead of JP Duminy - which may yet happen in Hamilton. Parnell, being a left-armer, offers a change of angle, which South Africa may feel they need at the moment, but that does not necessarily put him ahead of Morris or Olivier. Not yet, anyway. He still needs to prove his consistency has improved before he can be trusted as long-form player.

So, all things considered, there is a strong chance South Africa may end up using only half of the seamers they brought on this trip. But that doesn't mean it is an elite club that will never accept new members. It can't be that. They play 14 Tests in nine months from July - four in England and ten at home against Bangladesh (2), India (4) and Australia (4) and the last eight could be squeezed into 12 weeks early next year. They will need more than three quicks to carry that load.

Steyn is targeting a mid-year comeback with the England series firmly in his sights but he will need to prove his fitness, as Morkel did, over a sustained period of time. Although Morkel came into the New Zealand Tests with just two List A games under his belt this year, he played practice matches on South Africa's tour of Australia in October and November, and spent many hours in the Newlands nets, bowling to national players. That's how du Plessis knew Morkel was ready.

Whether Steyn will do the same in England remains to be seen. He may seek out a brief county stint in a bid to be match-ready. He may not manage that as soon as he would like. Whatever the case, South Africa will need other options.

Morris and Olivier should know that well enough and it seems they do. Though eligible by virtue of their scant Test caps, both players have provided separate assurances that they will not consider the Kolpak route. They need to remember, now that their Test careers seem to have stalled, particularly Olivier, who is not part of the limited-overs' plans like Morris, that the queue they are in could move very quickly.