In the final innings of the Test series in India, South Africa played in a manner only they could have done in this day and age. Their "blockathon" not only delighted purists but also showed why they are the best Test side in the world, for resilience is a virtue common to all great sides.

On the face of it, their effort looked like a case of mind over matter. In reality it's not so straightforward.

There have been many instances of batsmen digging in and playing an innings of steely resolve. Sachin Tendulkar's double-century in Sydney in 2003-04 is a fine example of the ability to control the mind. Once he decided he wasn't going to play anything on the off side off the front foot, he simply left everything outside the off stump to force the bowlers to bowl closer and help him score.

While Sachin's display of discipline was exceptional, it was still not close to the South Africans' effort at Kotla. In Sachin's case as much as it was about his discipline it was also about the limits of Australia's patience. The moment they ran out of it, they played into his hands. And he had to face only 25 to 30 balls at a time, not 200, as was the case with the South African batsmen in Delhi.

Also, though Sachin stuck to his plan, he didn't deny his basic instincts as a batsman to look for ways to score runs. His innings was about discipline, South Africa's about self-denial for a greater cause.

The difficulty in executing such a plan is that you're likely to misjudge the line and length, or both, when you're so focused on defence. Since you are so intent on your own plan, you tend to focus a little less on the ball

We often see batsmen mutter to themselves while setting up to play the next ball. They usually tell themselves to focus on the next ball (thereby allowing the body to just react), and to play the ball on its merit.

But the South African batsmen defied this conditioning to react to the ball and treat every ball on its merit. Since they had decided to block everything ball after ball, the only plan was to present a dead bat irrespective of where the ball landed.

That is tough.

The moment you see the ball leave the bowler's hand, your instincts take over - because that's what you have taught yourself over the years - and the body reacts. If the ball is full, the body moves forward. If the ball is short, the body moves backwards. And if the ball is there to be hit, you go hard.

But that didn't happen in Delhi. The South Africans didn't react to the ball, instead defending perfectly hittable or loose deliveries.

The difficulty in executing such a plan is that you're likely to misjudge the line and length, or both, when you're so focused on defence. Since you are so intent on your own plan, you tend to focus a little less on the ball. You can also get lazy as your stay in the middle is prolonged, even when bowlers start bowling way outside the off stump with a heavily guarded off-side field.

If you are bent on leaving everything that is not aimed at the stumps, watching the ball closely and covering the wicket all the time isn't a priority anymore. Similarly, if you are looking to defend everything, planting the front foot to a slightly short ball or going back to a fuller ball seems acceptable.

It was extraordinary that the South Africans didn't make any glaring errors of judgement for so long. Hashim Amla, Faf du Plessis and AB de Villiers' dismissals didn't occur due to a drop in concentration; it was that the wicket deliveries were just too good to be kept out.

This is a rare feat, but quite spectacularly, South Africa have done it in the past as well. They are the only team in the world who still possess this facet of play. Why is that so?

I discussed the subject in detail with Sanjay Manjrekar and Ajit Agarkar in our review of the series on this site. While we didn't have definitive answers, we did come up with a couple of theories.

Firstly, you need really strong defensive skills set to pull off such a feat. South Africa have that. Their pitches at home are among the toughest to bat on, so much so that the average of nearly every great batsman in the world is lower in South Africa than their career averages.

A strong defensive foundation is critical to survival on pitches that offer a lot to the bowlers, and perhaps that's why South African batsmen master this aspect of the game in their formative years. Technical competence over flamboyance seems to be their thing.

The second theory we came up with was that the apartheid era might have triggered a sense of urgency in their personality. Since many of these players grew up in a period where they existed in a bubble, they value the importance of an opportunity a lot more than the rest. Their doggedness might partly be the result of the time their team spent away from international sport.

You can apply one of these theories, or both or neither, to the innings in Delhi, but whatever separates the South Africans from the rest, it's worth holding on to and passing to the next generation. I hope that happens, because Test cricket will be poorer without these once-in-a-while blockathons.

Aakash Chopra is the author of three books, the latest of which is The Insider: Decoding the craft of cricket. @cricketaakash