Dean Elgar has a running joke about the number of opening partners he's batted with, but the reality is not very funny: since succeeding Graeme Smith at the top of South Africa's Test batting order almost six years ago, Elgar has had ten partners. That none of them have managed to stick around could well be the single-biggest factor affecting South Africa's batting, which is at one of its lowest ebbs.

Since their readmission, South Africa's top seven have collectively averaged less only three times - all after 2014. On one hand, that tells you how much South Africa lost when Jacques Kallis and Smith retired in the space of three months; on the other, it's the story of their struggle to find a stable top order, which is essential for batting success.

In scrutinising South Africa's under-performing line-up, the spotlight has been on the middle-order, where AB de Villiers left a Superman-sized hole when he took a sabbatical for most of 2017 and retired in mid-2018. Critics have noted the contrasting forms of Quinton de Kock, Faf du Plessis and Temba Bavuma and the inexperience of the players selected to bat around them. That has allowed Elgar to fly under the radar. But not anymore.

Although Elgar has scored one hundred and one fifty in his last 14 innings, he has battled along with the rest of them. His average has more than halved from 53.71 in 2017 to 25.07 in 2019. While there are some mitigating circumstances for his flailing form, including conditions and circumstances, which we will consider, there also obvious alarm bells in terms of shot selection and his approach to spin, which cannot be ignored. Primarily, though, South Africa's problems begin at the top, where the other opener has not been confirmed, something which has contributed to Elgar's woes.

Let's start with the arguments in Elgar's defence.

For too long, Elgar has had to be one opening batter acting on behalf of two, attempting to shield both South Africa's No. 3 and No. 4 from fresh bowlers and a new ball, because his partner was too junior (in age or cricketing terms) to be expected to do the same. South Africa cannot keep expecting that from Elgar without also expecting to affect his game.

Of late, South Africa has been among the tougher places in the world to open the batting because pitches have been lively and the ball has jagged around. The recent numbers, and anecdotes, support that. From January 2018, when Ottis Gibson took over, South Africa concentrated on creating conditions in which fast bowlers would thrive. Gibson and Faf du Plessis spoke candidly about their requests to groundsmen to prepare spicy surfaces and their desire for difficult pitches, especially against subcontinent sides. South Africa hosted Bangladesh, India, Pakistan and Sri Lanka and aimed to target all of them with short-pitched bowling on green tops, even if it came at the expense of their own batting averages. It worked - sort of - because since January 2018, South Africa has been the fourth-toughest place to open the batting, better than Bangladesh, England and West Indies, but well below New Zealand and India.

It's hardly surprising then that England have been the other team that has struggled to settle on an opening pair, and ironic that their solution came in the recent series in South Africa. In this light, it makes sense that Elgar's numbers have tapered off.

He's not been alone. Openers the world over have found it more difficult of late. And comparatively, Elgar has not been that bad since January 2018 (among openers to have played 15 innings or more).

If 2019, a year in which South Africa won just two out of eight Tests, lost to Sri Lanka at home and India away, has been especially tough for Elgar, it is because it has highlighted his vulnerabilities against spin. Over the course of his career, Elgar has been particularly troubled by offspin, falling to R Ashwin six times in nine Tests he has played against him, five times in ten to Nathan Lyon, five times in eight to Moeen Ali, and to Dilruwan Perera five times in four. This quartet are the top four most regular wicket-takers when it comes to Elgar in Tests. He averages 31.48 against offspin since his debut and in this England series, dominated by pace, Elgar was out three times out of eight to spin, twice to Dom Bess' offbreaks.

Like many in the South African line-up, Elgar's approach against spin is not always as decisive as it should be. He is often unsure whether he should take them on - and often does to detrimental effect - or bide his time. He is clearly uncomfortable with the ball turning away from him and if South Africa are serious about upskilling, as Mark Boucher has put it, this is one area that needs urgent attention because of the role Elgar has to play.

In the absence of de Villiers and Hashim Amla, and given the responsibility du Plessis has to shoulder as captain, Elgar is now the senior-most member of South Africa's line-up, senior enough so that some of his dismissals in this series have not best reflected that status. Playing shots like a whack to mid-off at Newlands, even after the importance of his 88, and the slice to point and lame pull at the Wanderers cannot be explained away with a shrug and a sharp turn of phrase. "Brainfarts" are funny occasionally but smelly most of the time and Elgar needs to start turning his nose up at them like the rest of us.

It's more likely he will be able to do that when he knows and trusts the person at the other end. Since Gibson, Aiden Markram has been seen as the preferred candidate for a long-term opener's role. However, his failure to progress from a strong start means South Africa have had to, and should continue to, look elsewhere.

Pieter Malan is their latest experiment and he made a promising start on his debut, before fading away. Malan has an excellent first-class record and probably deserves a longer run in the side. But with the way the results have panned out, you'd be forgiven for thinking he could go the way of Heino Kuhn, who played in one tour to England 2017 and then disappeared into a Kolpak-tinged sunset. Kuhn was 33 when he debuted, so Malan, at 30, may have more of a future, but South Africa could opt to change tack completely and promote a younger player.

Should that happen, and South Africa cast their net wider, they could do worse than give an opportunity to Raynard van Tonder or Eddie Moore, who sit first and second on this season's first-class run-chart. The former, who is 21, would be a long-term investment but even Moore, at 26, has several good years left to play. Selecting another opener may even make room for Markram in the middle-order, where so many top-order players, Elgar included, found their feet internationally.

What's important is that whichever route South Africa go, it is communicated to Elgar in a way that takes some of the pressure off him and convinces him that the load will be shared. For too long, Elgar has had to be one opening batter acting on behalf of two, attempting to shield both South Africa's No. 3 and No. 4 from fresh bowlers and a new ball, because his partner was too junior (in age or cricketing terms) to be expected to do the same. South Africa cannot keep expecting that from Elgar without also expecting to affect his game. They also have to acknowledge that Elgar deserves more.

He has been instrumental to the Test set-up since 2012 and, if du Plessis does not continue, could be the last link to the team that was No. 1 in the world. He will provide the experience the line-up needs to learn from and thrive. And he would probably like to do that with the certainty of one partner at the other end.

Firdose Moonda is ESPNcricinfo's South Africa correspondent