If anyone needed reminding of why out-and-out pace matters in Test cricket, Anrich Nortje did so vividly on the opening day of the second Test between the Proteas and Sri Lanka at the Wanderers on Sunday.
The 27-year-old quick spearheaded the dismantling of the visitors, who totalled a paltry 157 in their first innings after choosing to bat first, as he captured career-best figures of 6/56 in 14.3 penetrative overs.
That foundation was capitalised on by Dean Elgar and Rassie van der Dussen, who put on an unbeaten 114 for the second wicket as the hosts reached 148/1 at the close.
Elgar stole much of the batting show with an unbeaten 92 off just 116, while his partner finished on 40.
It wasn't really Nortje's wickets column that was the most important reasoning for having a bowler clocking upwards of 140km/h every delivery, rather the manner in which he took them.
On a Wanderers surface that will probably require a bit more sun to quicken up, Nortje's extra zip was vital, especially given the struggles of his less hasty new-ball partner, Lungi Ngidi.
This wasn't a pitch where 130km/h fare was going to get a bowler far unless he was supremely accurate.
That was evident in Wiaan Mulder's spell.
The 22-year-old Highveld Lions all-rounder continued his fine form with the ball, his spell of 3/25 opening the trapdoor that led to Sri Lanka's collapse.
Nortje did make the initial breakthrough when he had a stroke-less Dimuth Karunaratne (2) caught behind with a rip snorter that shot up from a short length.
South Africa then struggled to make headway after that as the freewheeling Kusal Perera monopolised the scoring for the majority of the first session, feasting on the home attack's willingness to allow him to hit through the line.
The hero of the Islanders' previous tour here in 2019 hit 11 boundaries in his 67-ball 60 as the run-rate edged past the four per over mark before Mulder made his appearance.
The 22-year-old Highveld Lions star, who actually labels himself batting all-rounder, struck twice in his second over as his splendid line had the Sri Lankans suddenly flustered.
He got a delivery to slant across the dangerous Perera, who got a thick edge to a half-hearted drive and then snapped up Kusal Mendis four deliveries later as the right-hander pushed hard at another ball that was exemplary in its line and length.
In his next over, he had Lahiru Thirimanne (17) caught in the slips after the left-hander shaped to play to leg.
From a position of relative strength, Sri Lanka found themselves in heaps of trouble.
Buoyed by Mulder's spectacular burst, Nortje took over.
He polished an excellent first session for the hosts by dismissing debutant Minod Bhanuka with some extra bounce that found the splice of the bat, before delivering his jackpot spell after the break.
Channelling his aggression far more efficiently than in Centurion earlier in the week, the Warriors ace varied his assault and reaped deserving rewards.
Adopting a fuller line, Nortje had Niroshan Dickwella caught off a booming drive after Quinton de Kock brilliantly dove in front first slip to hold a skilful catch.
He went shorter for his next two victims, Dasun Shanaka (2) and Dushmantha Chameera (22), who both strangely went for reviews before he comprehensively castled last man and debutant Asitha Fernando.
It was a spell that enviously combined power with precision.
The Sri Lankan bowling, despite some decent spurts by Asitha (1/30) - who claimed Aiden Markram as his first Test wicket - and a good first spell by Dasun Shanaka, lacked similar inspiration.
Elgar was typically ruthless on the on-side, where he used his customary flick to good effect, though his off-side play didn't lag too far behind.
He found a good ally in Van der Dussen, who showed rare mental steel in shrugging off the 26 deliveries it took for him to get off the mark to his six fours in what became a progressively more fluent innings.