As England trouped off the field at lunch on the third day in Johannesburg, with the game in the balance and the bowlers struggling to find the correct length to exploit the bounce and cracks in the surface, Trevor Bayliss produced what may come to be the defining moment in his career as coach.
It wasn't that Bayliss said anything particularly revelatory or inspirational to the team. And it wasn't that he shouted and ranted in a way that shocked or rebuked.
It was that he had waited to make a contribution and then chose his moment and message perfectly.
Compare that to the methods of his predecessors. By the end of Andy Flower's period as coach, he so intimidated some players that his attention seemed to stifle rather than assist. And Peter Moores, for all the good intentions, was said by some players to be prone to talking a little too much and, as a consequence, diluting his message.
There's something of the constitutional monarch about Bayliss: you can sort of understand why you need someone in the position, but you're not always sure exactly what he does. His old-school cricketing philosophy means that the captain is always the man in charge and, in training, it is his genial assistant, Paul Farbrace who appears to inject the energy and organisation. And Bayliss is far too much of a fair dinkum Aussie to bother to cultivate a media image.
But he does know about cricket. Indeed, those that know him best suggest that, when he is looking for variety, he stops thinking about international cricket and starts to think about county or state cricket instead. And when he tires of that, he thinks about club cricket.
So when he spotted some warning signs in Englands's performance early in South Africa's second innings - the bowlers were pitching too short and the fielders looked ready to sit in for the long haul rather than keen to divert the natural direction of the game - he knew it was time to act. He rejected Alastair Cook's suggestion that he gave the team "a kick up the arse" but accepts he was not fully satisfied with what he saw.
"It was more of a reminder, I suppose, of what we needed to do help the bowlers win the game," he said. "I wouldn't class it as a kick up the backside. But I thought before lunch and even in the first innings their attitude was not quite right in the field.
"Out in the field it was a little bit quiet. There was no movement.
"It's always a decent attitude, but to field well and pick up those half chances - we missed a few in Cape Town - the energy and the attitude has to be more full on.
"So it was just a bit of reminder that if we want to win this Test, now is the time to hunt in a pack or get in the batters' face. Try to make them feel 'where's our next run coming from?' and help the bowlers put the pressure on.
"We had spoken about it in the past. But they are only young players, most of them, and like any young person you have to remind them now and then. A player has actually got to make mistakes to learn from them. If someone is telling them all the time what to do then they don't necessarily recognise it themselves. Hopefully it is a lesson learned and hopefully as time goes by they won't need a gentle reminder."
While Bayliss cannot have predicted how dramatic the results of his "reminder" would be - and 10 wickets in 25.2 overs is pretty dramatic - he clearly has a huge amount of confidence in the potential of his young squad.
"This team could turn into something special," he said. "You look at some of those players with 50 or 60 Tests experience under their belt and the potential is there. If we win a few Test matches there'll be a chance of going up the rankings and becoming the best team in the world.
"But potential never won anything. You have got to go out and do the hard work and not take everything for granted. I still think we're two or three years away from possibly our best period."
Central to progressing, in Bayliss' view, is an improvement in England's fielding. Not just in the Test side, either, but throughout the game in England and Wales. It is, he believes, one area in which England lag behind Australia.
"I'd like to see - in general - our fielding improve," he said. "That's not just at this level but at county level as well.
"If you think of the game of cricket from a batter's point of view, they probably spend 85-90% of the time they are actively in the game fielding. So we have to do a bit more work on fielding.
"There always seems to be a lot of batting and bowling technique work, but there probably needs to be a little more technique work done with fielding as well.
"It's probably one area of the game that is different between Australia and England. Australian sides do more fielding technique work at a younger age."
That fielding work will have to wait a day or two. Having earned a couple of days off, England will not train again until Wednesday. By then, they will have decided whether to send the injured Steven Finn home - it looks likely that his tour is over - and whether to recall Chris Woakes for the final Test or give a chance to the uncapped left-arm seamer Mark Footitt. Woakes is the more likely choice; England are not in the mood for experimenting.
"We want to win 3-0," Bayliss said. "If you want to get to the best team in the world, you win series three, four and 5-0. That's the challenge for these young blokes."