If a brain fart had an odour, it would be what Quinton de Kock smelt like after he hit a Joe Denly long-hop straight to midwicket in the post-tea session. It would reek of regret, pong with impatience and give off a whiff of what-could-have-been.
It lingered in the Newlands air, with the inevitable realisation that even South Africa's longest fourth innings in more than four years was not enough to hold onto their series lead. That was long after Dean Elgar's self-confessed first-innings "big one" and de Kock's more recent fluff.
De Kock is not the batsman South Africa would have expected to be at the forefront of a block-a-thon, especially after he flicked the first ball he faced fine for four, but he has never scored fifty runs slower in a Test than he did at Newlands. His relative restraint against the spinners, especially with the ball spitting out of the rough outside his offstump, suggested a maturity de Kock has previously been thought to lack. He spent two hours and nine minutes at the crease, faced 107 balls and did not score off 83 of them.
"He was going really well and we felt he had it under control," Faf du Plessis said. Until that long-hop. De Kock could have hit that anywhere and he knew it. As the catch was claimed, de Kock stood motionless in disbelief, both hands on the top of his bat handle, a slight squat to his stance, in a position that said "oh no."
His was the first of five wickets South Africa lost for 11 runs in 17 overs to fall 50 balls, or maybe 40 minutes, short of saving the match. While de Kock's wicket added the final stench, the fumes emerged much earlier.
If a brain fart had a smell, it would be what du Plessis smelt like after he swept Dom Bess straight to square leg having batted with restraint for 57 balls, with memories from Adelaide 2012, Johannesburg 2013 and Colombo 2014 mushrooming. Du Plessis doesn't need to listen the war stories, he was on the front line on all three occasions. If there was one player in the South African XI that the rest would have bet their houses on to secure the draw, it would have been du Plessis.
For 79 minutes, he absorbed pressure, most of the time showing only defensive intent. As deliveries from James Anderson jagged off the seam, du Plessis dead-batted them to put himself out of harm's way. He played one risky shot - a splice over gully - and one aggressive shot - a drive through point, and was readying to take the shine off the second new ball. But, 3.4 overs before it was due, Bess dangled a delivery outside off, du Plessis went at it with hard hands, thinking it would go over the fielder, but found him.
"With everyone around the bat, with square leg and midwicket up, I [was trying to] go over the guy. To sweep it in the middle, was a mental error," he said. "When you have a few guys around the bat and the ball spinning out the rough, you try and manipulate the field a little and spread it but all we needed was for me to drop anchor."
That may not be where the match was actually lost, however.
If a brain fart had a smell, it would be what Elgar smelt like after he threw away a beckoning hundred and a strong position in the first innings when he mowed Bess to mid-off. South Africa had recovered from 40 for 3, to 157 for 3, Rassie van der Dussen had bedded in and a partnership was developing. Though the first innings seems like an unfair place to start working through the fog of this defeat, it is actually where the indigestion came from.
South Africa were building the foundations of a lead before they lost 7 for 66 and conceded a 46-run first-innings deficit. Elgar's dismissal sparked the collapse and though blame cannot, and is not, being laid at one player's feet, Elgar knows he got that wrong. So do the rest. Asked where the game was lost, du Plessis said: "First-innings runs. We got ourselves into a position where we should have got a little bit more."
All that means the performances of the senior trio in South Africa's top six will have wrinkled a few noses and furrowed a few brows while the men themselves will look at their junior members and blush. Pieter Malan on debut, Rassie van der Dussen in his second Test and to a lesser extent Zubayr Hamza in his fourth all showed the temperament the situation demanded. Malan played a knock that may confine Aiden Markram to the domestic system for the foreseeable future, van der Dussen has almost certainly laid claim to the No.5 spot and Hamza's technique should set him up for a long stint at No.3.
The new players are what du Plessis said is "needed for us to move forward. You need guys to come through in a transitional period and put their hands up and say, 'I am going to make this spot my own.'" The same thing is happening to England, where Dom Sibley's century changed the complexion of the game.
Before this series started, it was seen as a contest between which problem-riddled line-up could cobble together more runs, with good reason. Since the beginning of 2019, England have played 25 Test innings and being bowled out for less than 300 some 15 times, including nine scores under 200. South Africa have batted in 18 and been dismissed 14 times for less than 300, with five scores under 200. Compare that to India, who have only been bowled out twice in 11 innings over the same period, once for under 300, and Australia, who have had five out of 23 innings under 300, and you will understand why the ICC Test Championship points table looks the way it does.
While England's 2019 was studded with batting blowouts, South Africa were consistently poor. The former speaks to issues in approach, the latter, issues of personnel. Already, though, both problems have showed signs of being resolved. In South Africa's case, it may even be the turning of a corner.
"Two months ago, we were very weak mentally. We exploded quickly. Sometimes you will improve by losing," du Plessis said.
So maybe if a brain fart had a smell, it would not be as putrid as it sounds. It may carry the scent of change.