Cape Town - South Africa's preparations for the 2019 World Cup have centred around their bowling attack. 

Skipper Faf du Plessis has said as much, several times. 

Where other teams will be backing themselves to post and chase scores in excess of 350, the Proteas will be looking to bowl their opposition out and win games that way. 

It is a major part of the reason that batting depth has been such a concern heading into the tournament. 

Numbers 8, 9, 10 and 11 in South Africa's World Cup batting order, if everybody is fit, will almost certainly read: Rabada, Steyn, Ngidi, Tahir. 

There is obviously not much there in the way of potentially game-changing innings, but that is where the Proteas are looking to do their damage. 

Lungi Ngidi is receiving treatment for a side strain and is reportedly well on track to make the World Cup while Dale Steyn has his feet up after a decent stint for the Proteas against Sri Lanka and for the Titans in their One Day Cup exploits. 

Imran Tahir and Kagiso Rabada, meanwhile, are at the IPL. 

Cricket's most lucrative spectacle was always going to be a painful one for the Proteas to digest with the World Cup in mind, and there is no doubt that coach Ottis Gibson would rather have Rabada and Tahir wrapped up safely at home.

Rabada is the tournament's leading wicket-taker with 11 from 6 matches, while Tahir is also high up on that list with 7 from 5.

The signs, particularly in Rabada's case, have been exciting from a South African perspective and his 4/21 against the Royal Challengers Bangalore on Sunday was indicative of that.

He is striking against some of the best batsmen in the world – he removed both AB de Villiers and Virat Kohli on Sunday - and he has also delivered at the death in high-pressure situations.

Perhaps most pleasing, though, is that Rabada has his yorker back. 

It has always been a favoured weapon for the 23-year-old, but over the last year or so his execution of the delivery has not been at its best.

In that sense, the IPL has been the perfect platform for Rabada. 

When he gets his yorker going at the speed that he naturally possesses, Rabada becomes one of the deadliest bowlers in world cricket and that is exactly the space the South African brains trust need him in heading to England. 

Throughout his career, and especially in those early years, Rabada's hunger for the game and a desire to keep bowling squashed any suggestions of possible rest and his workload has always been an area for concern.

That is very much the case once again. 

It is only T20 cricket and four overs per game should theoretically be fine, but the travel and training in between the fixtures also play their role. 

Rabada has played all six of Delhi's matches in IPL 2019 and has travelled to four different cities in just two weeks. 

The scheduling, the travel demands and the relentless hype that surrounds the IPL from beginning to end all combine to make it a draining experience - physically and emotionally - for the players and that is obviously the last thing the Proteas need when it comes to Rabada. 

Like Quinton de Kock can win games by himself with the bat, Rabada can with the ball, but not if he is running on half-empty. 

It must be a worry.

Right now, Rabada looks like he is peaking, but if you are one of those holding your breath every time he glides into the crease, then rest assured that you are not alone. 

His fitness for the Proteas is paramount to the point where it is hard to see South Africa making a play at becoming world champions without him.

He is that important, and in that regard, the IPL can't end soon enough ... 

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