With massively proven names like Graeme Smith, Hashim Amla, Jacques Kallis and AB de Villiers, South Africa's batting at Test level should be a thing of beauty and brutal efficiency. On paper, it is right up there with England, India and others. Between them, that core quartet alone offer 369 caps and a lofty combined total of 29,118 runs.

Only Kallis, at 36, is almost certainly past his prime; Smith may be just about at it, and both Amla and de Villiers may only be approaching it. Yet in delivery as a collective this season, South Africa's frontline batting has receded to the point that it can pretty much be described as "vulnerable". That's how far its stocks have mysteriously tumbled.

The situation is not helped, of course, by ongoing uncertainty around one of the opening positions, and the fact that, as things stand, every batting slot from No. 6 to 11 boasts at least some discernible degree of weakness to arouse the opposition into believing the team that might - and should - be giants can be slain.

Sri Lanka discovered as much to their unbridled glee when they thrashed South Africa in the second Test at Kingsmead on Thursday for one of their finest wins and one of the host nation's most ignominious losses - certainly on home soil, at any rate.

There should be quite enough class in the South African batting order for it to be purring like the proverbial machine, not unlike the golden Australian phase of Messrs Hayden, Langer, Ponting, Martyn, Waugh and company. Why it palpably isn't is clearly going to be one of coach Gary Kirsten's greatest challenges.

Somehow South Africa are finding it a grim old struggle this season to put together big totals - especially in the bedrock, all-important first innings - as their largely impressive parts fail to translate into a compelling whole. Numbers don't lie: only once in four first innings on home soil this summer have South Africa managed to bat into deployment of a new ball, the quartet of totals reading: 96 (Newlands) and 266 (Wanderers) against Australia, and 411 (Centurion) and 168 (Kingsmead) against Sri Lanka. Even in the 400-plus effort at SuperSport Park, mind you, South Africa were a rocky 173 for 5 before they translated that into something a whole lot healthier.

By contrast, there is little wrong with the bowling, and the spunky determination of champion strike bowler Dale Steyn to blossom into anything but a bunny amongst a still-too-fluffy tail is just an additional example to those around him. But it is with the blade that South Africa may have bigger problems than they are currently conceding, and why many of us are a tad more nervous than we initially expected to be about the team's ability to clinch the series at Newlands over the New Year.

As things stand, too many of South Africa's kingpins at the crease are firing only fitfully and, just as often, showing a disconcerting new penchant for getting out after getting in, lapsing in concentration after breaks, and failing to assemble the sort of marathon partnerships that were almost a fait accompli a year or two ago. Into the bargain a few of them suddenly look more skittish than usual against short-pitched bowling - even from the moderate Sri Lankans - although perhaps that is simply a personal gut feel.

A glance at the recent form - that word is used cautiously - of the top seven who did duty in the Kingsmead pummelling tells you everything you need to know about the attack of the "yips" that has seemingly infiltrated the cause. The captain, Smith, remains in a long-standing erratic pattern, although he at least boasts a century just a few weeks back, against Australia, at the ground where South Africa are about to fight for the preservation of their dignity.

Somehow South Africa are finding it a grim old struggle this season to put together big totals - especially in the bedrock, all-important first innings - as their largely impressive parts fail to translate into a compelling whole

Incumbent partner Jacques Rudolph has frankly seldom seriously looked the part alongside him, having scratched his way into the teens, twenties or thirties before succumbing just as he has seemed poised to negotiate the new-cherry storm. Maybe, as rumoured, an ongoing challenge will be found for him a few notches lower. There are still plenty of people who want to see the unassuming left-hander succeed anew for his country.

The Nos. 3 and 5, most of the time, Amla and de Villiers, are perhaps most comfortably absolved from responsibility for the present frailty: Amla got two centuries against Australia and back-to-back fifties in the most recent Test in Durban, while the latter has shone at least once at the crease in three of the four home Tests thus far while never quite managing to go to three figures.

And speaking of centuries, one of those still eludes the mighty Kallis in South Africa this campaign. With one Test to go - fortunately at his fruitful, much-beloved Newlands - he has a last opportunity not to fail to post a home ton for the first time since 2006-07. He will not need reminding that his 2011-12 scores thus far have been, in order, 0, 2*, 54, 2, 31, 0 and 0. It is the sort of (highly unusual, let's face it) ammunition that will be seized upon by harsh pundits as their "evidence" that the old master's physical and mental powers are fading. For the record, I'm not in that camp yet. All batsmen can and do fall prey to bad trots, and Kallis may simply have caught the under-performance virus at the crease.

Ashwell Prince? Like Rudolph, he has failed to look commanding, with a meagre lone half-century to show from his last six Test matches.

All these iffy displays up top have only made the situation at No. 7, where gloveman Mark Boucher clings with typical stubbornness but no great assurance to life, look that much more brittle. I have been an unashamed Boucher fan for many years, and still am to a good extent, but the old cliché employed by commentators in his defence of "Ah, at least he's a fighter" is beginning to irk just a bit, not least because we see those gladiatorial qualities less and less these days.

Contentiously, considering the long, long spell in which South Africa have been lamentably inconsistent, the selectors have resisted the temptation to alter the batting department to any great degree for Newlands, simply keeping Alviro Petersen "thereabouts" and in with a shout at recall for the Cape Town decider. If I were any of JP Duminy, Dean Elgar, Morne van Wyk (psst, not the world's worst wicketkeeper, for those who may have forgotten), Colin Ingram and one or two others, I might be getting a little restless right now, and perhaps with good reason.

Mind you, knowing South Africa, they will probably go and blitz Sri Lanka with the staffing they've got in Cape Town. And, at least to a blinkered few, all will seem blissfully hunky dory once more as they heap contempt on those of us who had the audacity to throw eggs at an increasingly too inflexible Fort Knox.

The article was first published on Sport24.co.za, where Rob Houwing is chief writer