Cape Town - It's been as good a reason for a collective, disbelieving and dejected dropping of jaws among South African sports fans as the events in Brighton at the 2015 Rugby World Cup.

The Springboks' tournament-starting 34-32 defeat to minnows Japan on September 19 that year is widely regarded as the unlikeliest high-profile team-sport humiliation in the country's history; I'd say the two-match sting from Sri Lanka, traditionally so fragile in the southern hemisphere, over the past fortnight either matches it or at very least runs it desperately close indeed.

The lower mid-table tourists in the Test format only bloodied the Proteas' noses further on Saturday as they not only won the second clash in Port Elizabeth to secure the series 2-0, but did so in a single-session blaze of nerveless, audacious stroke-play from overnight pair Kusal Mendis and Oshada Fernando.

So as much as the series in total almost certainly represents South Africa's poorest in post-isolation home history, the St George's Park loss by a gaping margin of eight wickets - and in just two and a third days - also warrants going down as extremely hard to eclipse for rank ineptitude on their part.

It was also, in what might be termed a grim cherry on top of the unpalatable cake, the second time in as many Tests where the much-vaunted Proteas bowling attack has taken some pretty contemptuous "tap" toward the key, back end of the match.

Perhaps the bowlers can be more excused, though: white flags have far more frequently been run up by the batting department in recent months - it has become the overwhelming, prime area of concern - and the likes of Kagiso Rabada, Duanne Olivier and company must have been extremely close to a toss-away-the-tools-in-protest sort of feeling, if they hadn't already.

While making the point afterwards that he did not wish to submit it as an excuse, a clearly hurting captain Faf du Plessis virtually did anyway by implying in his pitch-side television interview as the dust settled that long-season syndrome for his charges might have come into play in the shock match and series result.

But it is hard to feel any major sense of sympathy on that score when you consider how much more travel-weary the giant-slaying Sri Lankans warrant having been.

They arrived in the country at indecently short notice - a budding trend globally these days, mind - having just suffered successive away series losses in both New Zealand and Australia.

After a draw in the first of two clashes with the Black Caps, they were then pulverised in the decisive second encounter, and suffered heavy losses in each of the pair of Tests against an Aussie outfit riddled with self-doubt and selection instability in the lead-up, after their own home series reverse at the hands of India.

So yes, throw in the fact that their record on South African soil has previously been so feeble, and Sri Lanka were rightly deemed heavy underdogs against a Proteas side who had just seen off Pakistan 3-0.

Incredibly, they now stand handsomely instead as the first Subcontinent team to win a Test series here (after 21 failed earlier attempts split between the relevant four nations) and just the unlikely third country worldwide, outside of longest-standing foes Australia and England, to do it.

What's more, the 'Lankans can now claim another significant statistical landmark against South Africa: first ever opponent to be able to boast clean sweeps of each of the last home and away series between the specific countries in question, considering that they won a similarly two-Test series on Sri Lankan turf in 2018 also by a 2-0 margin.

With Saturday's earth-shattering result, the Proteas automatically slip a peg to third on the ICC rankings, now behind both leaders India and those rare eclipsers of them, New Zealand.

It will be a fair while before they are in a position - much soul-searching is required in the meantime, especially in terms of both personnel and shape of their rickety batting arsenal - to claw back ground, and cynics will say that is unlikely with any stealth anyway, as an away series against the undoubtedly premier Indians is the supposed next on the Test roster in October.

Indeed, that shapes as such a formidable challenge, bearing in mind the 0-3 drubbing last time there, that it might be wise for Cricket South Africa to try to squeeze in another short series or even once-off Test against a more moderate power ahead of it.

That would at least enable any new faces - and a clamour on that front is only likely to intensify, given the increasing weight of statistical under-deliverers in the team - some sort of opportunity to find their feet at the highest level before the Indian mission comes around ...

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