Usually reasonably shielded from the hazards of the new ball, yet also not low enough in the order to face the risk of running low on sturdy partners, it tends to be the perfect berth from which to knuckle down for a “biggie” in multi-day formats.
That is why, over the past few decades - admittedly also a period marked by the dormancy of isolation - men like Graeme Pollock, Daryll Cullinan, Jacques Kallis, and also Hashim Amla for a self-favoured period while he was national captain, have been prior bastions of solidity and consistent statistical success there.
In short, you want a pretty proven “rock” in the position.
So there were plenty of surprised murmurs among observers when the Proteas handed JP Duminy, his very place in the XI under a cloud through recent under-performance, a promotion to No 4 on day one of the first Test against New Zealand at Kingsmead on Friday.
The diminutive left-hander, not exactly producing major scores at five, six or seven – he had one half-century, against minnows Zimbabwe, from 14 Test innings ahead of the latest one – hardly seemed tailor-made for elevation.
Yet he took guard at the fall of the second Proteas wicket, significantly ahead of acting captain Faf du Plessis who had been widely expected to fulfil the chore.
You would like to think it was a case of thinking out of the box -- and in fairness South Africa have been accused before of inflexibility and lack of initiative, so they might protest about a “damned if we do, damned if we don’t” kind of unfair judgement in this instance.
Nevertheless, the only feasible explanation to stalwart commentators like Kepler Wessels seemed that the host team wanted to maintain a left-right combination at the crease to try to unsettle the Black Caps’ attack.
As it turned out, too, the move could fairly emphatically be said to have bombed as Duminy, after champagne boundaries via a straight drive and hook, was suckered into a soaring pull soon after lunch and caught on the fence for 14.
As happened several times during a frustrating day for SA enthusiasts, it occurred just when the Proteas seemed tantalisingly set to seize at least a partial grip on proceedings.
Instead they looked the second-fiddlers at stumps on 236 for eight after winning the toss on a surface which, based on the imperious stroke-play on occasions of Amla and Temba Bavuma (best contributors with 53 and 46 respectively) seems better than that for run-scoring potential.
The average total batting first at Kingsmead is 301, so they will do very well to hit that mark from here, with only Dale Steyn, Kagiso Rabada and last man Dane Piedt remaining to engineer the quest.
The Proteas certainly aren’t in an iffy position simply because of the decision to crank Duminy up the order – there were several dismissals marked by impetuosity - but it is still a justifiable talking point.
We know he can play a bit, and every now and then even a lot, but the Test landscape continues to be too doggedly one in which he labours to cut it from a weight-of-runs perspective.
Following Friday’s latest flop, his average after 34-and-a-half Tests has dipped to 31.93 and that hardly seems a figure that cries out “No 4” invitingly.
Perhaps it was based on some kind of hunch, either by him or someone else of influence in the camp, that he might flourish again in that berth after doing notably well in a lone prior Test there against the same foes in Wellington in 2012 – Duminy scored 103 and 33 not out.
But his batting at Test level has looked shaky and indecisive for the most part since, regardless of position in the order, and he barely seemed ready or suited to fill the blue-chip slot anew.
Wessels’ SuperSport co-commentator Robin Peterson, himself a seasoned former international, suggested that perhaps Duminy batting at four is a sign that when regular skipper AB de Villiers returns to fitness, he will wish to occupy No 5.
And perhaps that is a dinner-table conversation all of its own?
our chief writer on Twitter: @RobHouwing