Cape Town – Amidst the sea of experimentation, one thing stood out as a regular hallmark of South Africa’s game-plan in their hot and cold one-day international series triumph in Sri Lanka.

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The Proteas, in all but one game of the five-match roster, employed a relatively novel formula (at least for them) of using Andile Phehlukwayo and Wiaan Mulder, both essentially little more than medium-pacers, as their first- and second-change bowlers.

Only once was there a slight deviation from the principle, in the fourth clash at Pallekele where Phehlukwayo was called to first duty behind the new-ball pair and occasional off-spinner JP Duminy entered the attack at the other end before Mulder did.

Otherwise, though, the young duo of bowling all-rounders were entrusted with considerable responsibility with the ball throughout the series, eventually won 3-2 by South Africa who lost some sting from a handsome 3-0 cushion at one stage.

Although the main objective of beating the Sri Lankans was achieved, and the last two games were played minus the services of regular captain and blue-chip batsman Faf du Plessis, it must be remembered that the host nation have hardly set the ODI planet alight in the past year or two.

They are down in the bowels of the ICC rankings at No 8 and entered this series not having won in eight prior bilateral ones.

So even after the embarrassing events of the Test series immediately preceding it, the Proteas prevailing in the ODIs by a tight margin should really be viewed as little more than a par performance.

That said, this is a phase of liberal experimentation, with the 2019 World Cup firmly in mind, so coach Ottis Gibson and company have been unashamedly fiddling with combinations and tweaking the XI regularly, which is not always a recipe for unrelenting success.

Clearly, in terms of his back-up seamers to the opening pair, Gibson was happy to thrust Phehlukwayo (still only 22, despite now holding 30 caps) and the 20-year-old greater novice Mulder into roles of appreciable, regular responsibility over the last couple of weeks with longer-term curiosity in mind.

Now … did it work out, and is it a brew worth persevering with?

A personal suspicion -- and one generally backed up by the statistical evidence from the series -- is that the Proteas will require a little more in the way of both penetrative qualities and discipline immediately behind the main strike bowlers (usually fronted now by Kagiso Rabada, with Lungi Ngidi making pleasing strides too).

In short, there is still room for a Dale Steyn or Chris Morris – both notably livelier in pace -- to come into the bowling picture, even if that might mean one of Rabada or Ngidi dipping down to the first-change position which is not exactly an unorthodox berth for many, highly-valued fast bowlers in the 50-overs arena.

Nearer CWC 2019, too, Vernon Philander may well come back into the equation as his ability to move the ball sharply both ways off the seam simply cannot be pooh-poohed for a tournament staged in English early summer; he would also provide the lower-order batting with a sense of technical correctness and perseverance it currently lacks too glaringly.

That could well mean, then, that over the next few months we see Phehlukwayo and Mulder, more and more, potentially scrapping for just one slot in the team between them -- if they even prove suitably worthy of ongoing presences in the broader squad.

Based on what we saw in Sri Lanka, both still have shortcomings in all areas of their cricket despite the gifts of almost undoubted, raw talent: the key will be whether that talent blooms enough in the lead-up to the World Cup.

Neither really caught fire with the bat, Phehlukwayo sometimes looking just too keen to bludgeon every ball when some sense of temperance was called for, and Mulder not yet proving, by contrast, that he is a genuinely powerful enough striker at this level.

But the jury is also very much out over their bowling displays – the area both got much more scope -- during the series.

The tracks tended to be favourable ones for batsmen, although there was a bit more carry and bounce at times than the Proteas might have been expecting, so it not as though seam bowling was an enduringly thankless cause.

Under the circumstances, then, Phehlukwayo and Mulder slightly underwhelmed.

The former, who should be getting increasingly consistent, took considerable tap despite being South Africa’s second-highest wicket-taker (nine) behind Ngidi (10).

While he deserves kudos for unflinchingly being prepared to “mix up” his deliveries, the KwaZulu-Natalian travelled at a bloated rate of 7.25 runs to the over – the Proteas’ most expensive bowler -- despite averaging a respectable enough 28.22, whereas Mulder sported marginally better economy (6.80) but also had to work harder for his five scalps (average 40.80).

Several colleagues boasted considerably better control of the white ball, including Rabada and spinners Keshav Maharaj and Tabraiz Shamsi, who all kept their series runs concessions to under five per over.

The Proteas’ “support” seamers?

You might just have to remain at that drawing board, Mr Gibson …

*Follow our chief writer on Twitter: @RobHouwing