The build-up to the three Kagiso Rabada overs that changed the course of the Johannesburg Test perhaps raises more questions than answers about the leader of South Africa’s attack. After bowling too full to Mayank Agarwal early on with the new ball, Rabada was taken off the attack by the seventh over and brought back by the 15th.

Even at his worst, Rabada tends to be South Africa’s best hope in strife, and Dean Elgar knew it. He produced a probing first over that promised much, only to lose radar with a half volley which was driven for four by Ajinkya Rahane off the first ball next over. And then he overstepped. He would go on to overstep off the first ball of his next two overs, separated by a night in between.

Rabada’s no-ball issue is no secret. According to ESPNcricinfo, he has overstepped more than any other bowler in international cricket since 2019. It’s sort of coincided with his decline in Tests as a bowler.

Since his debut in 2015 and before the start of 2019, no bowler except Rabada, who bowled in at least 15 innings clocked a strike-rate lower than that of 40. The seamer had taken to international cricket – Test cricket specifically – with remarkable ease. At the end of 2018, two and a half years into his Test career, Rabada had nine five-fors, one more than Morne Morkel managed in his entire career. He also had an exceptional bowling average of 21.5 and his bowling strike-rate of 39 was the best for anyone to have bowled 4,000 or more balls in Test history at the time.

Since 2019, though, Rabada has fallen off the top brass of international bowlers, partly also due to the two back injuries sustained in 2018 and 2019. It’s not that his numbers have taken a serious toll as is often made out to be. His bowling strike-rate since 2019 is still a very healthy 45.4. At home, it’s still below 40, with his average just over 24. Of course, they aren’t as good as they used to be, but it’s only natural that he regressed from what was an extraordinary start to Test cricket.

But there’s an evident lack of intensity that made Rabada a feared proposition in his early years. The on-off spells became all too familiar: the sight of him going from losing his radar entirely to rediscovering it in another spell soon after, became the norm. It coincided with a period where he, still developing into a world-class bowler, had to be the leader of the attack, with South Africa losing the likes of Dale Steyn and Vernon Philander. All of a sudden, Rabada went from the impact seamer to the responsible leader of the pack, and it’s a transition that’s still ongoing.

“Bowl 3 overs in a row like that and I GUARANTEE you’ll get a wicket” – Dale Steyn tweeted soon after Rabada’s intensity surged up at the Bullring on day three, even as the Cheteshwar Pujara-Ajinkya Rahane partnership soared. It’s not that Rabada does not know it. He most likely does. When he found his rhythm, in three overs, like Steyn tweeted, he changed the course of the game – Rahane, Pujara and Rishabh Pant were sent back with India’s lead just a shade over 150.

Bowl 3 overs in a row like that and I GUARANTEE you’ll get a wicket.

— Dale Steyn (@DaleSteyn62) January 5, 2022

“Good players pick up the pattern that works and zone in on it. Like a predator on the hunt, killer instinct focus! KG you beauty!” – the next Steyn tweet comes in, exactly 40 minutes after his first with the Rabada mayhem separating the two.

The spell is an indicator of what Rabada can do when he’s on song. Few fast bowlers in world cricket can match that intensity with wicket-taking ability. The No.1 ranked ICC Test bowler Pat Cummins is one. Since his return to top-flight cricket after a six-year hiatus with injury, Cummins has been the face of fast bowling – clocking an average of 21.3 and a strike-rate of 46.8.

More than the numbers, Cummins’ forte is his relentlessness. Nothing reveals this as much as the second innings spell at the MCG last week where he bowled 10 wicketless overs, yet spearheaded England’s collapse to 68 all out. After nearly taking out Haseeb Hameed’s head with his first ball, Cummins went on to work over Zak Crawley and Joe Root. The wickets came at the other end, but Cummins had laid the plot out perfectly with a 10-over new ball burst either side of a day.

It’d be a stretch to suggest Cummins can maintain his ridiculous career numbers once he plays more around the globe. 33 of his 37 Tests have come in Australia, England, and South Africa. He’s never played in West Indies, Sri Lanka, Pakistan, or UAE. Those numbers might even out a tad at least then.

It’s worth noting that nine of Rabada’s 10 five-fors came in the 2016-18 period when he hit his top gear more often than not. Wickets have still come in clusters as they did in Johannesburg, but doing it spell after spell, Test after Test is what separates Rabada from the No.1 Test bowler in the world.

But Rabada has ticked off a few small checkboxes as a 26-year-old already. He’s played in eight different countries and shown he can be menacing across all conditions. It’s the sort of interminable persistence that Cummins brings to the table that South Africa seeks from Rabada, only because he has done that in the past.

It’d be ridiculous to think Rabada is not capable of it. As much as he remains an impact bowler, Rabada’s discipline and thought process when he gets his rhythm right point to a sharp cricketing brain. That his numbers haven’t fallen off the cliff despite his tendency to go wayward every now and then, is as good a pointer as any about what Rabada can be if his ability marries consistency.