Before Kagiso Rabada became a household name, he made his first mark on the global stage at the 2014 Under-19 World Cup in the UAE.

His six-wicket haul against Australia, in the semi-finals, gave South Africa the momentum going into the final, where they beat Pakistan by six wickets. He ended the tournament as its second-highest wicket-taker, and that 2014 Under-19 triumph remains South Africa's only World Cup win across all levels and genders.

Three months later, he was awarded a contract with the Lions, and before 2014 was over, he had made his international debut in a T20I against Australia in Adelaide. He would soon be part of South Africa's ODI and Test teams too, and from there there's been no looking back.

But not everyone from that winning squad has made the same sort of transition into the top level. Barring Aiden Markram and Andile Phehlukwayo, no one else has played for South Africa in the six years since. Bradley Bopp has played no senior cricket - first-class, List A or T20. Greg Oldfield hasn't featured at senior level since 2014, while Bradley Dial last played in 2016. The list only gets longer.

According to Rabada, what sets players apart after their graduation from the Under-19 level is how much confidence they have in their own abilities.

"I guess it's not something you want to tell them, but not everyone can make it," Rabada tells ESPNcricinfo. "You have to have the belief to push through.

"It's one thing saying you believe in yourself, but you need to look inwards and ask yourself, 'do you really really believe in yourself?' That's what separates the players who make it and those who don't. Obviously, there's the thing about talent, hard work and focus, but self-belief is what carries you through from the Under-19s."

South Africa are currently playing the fourth Test against England in Johannesburg, which Rabada has been suspended from, for disciplinary reasons. It's why he's at Bloemfontein's Mangaung Oval, watching South Africa's Under-19s play UAE in their final group-stage game.

In the Port Elizabeth Test, Rabada had earned his fourth demerit point in the last 24 months for his celebration of Joe Root's wicket. The match referee had pulled him up for "using language, actions or gestures which disparage or which could provoke an aggressive reaction from a batter upon his or her dismissal", and Rabada had later said he "felt hurt" for letting the team down.

But Rabada maintains that passion, if channeled properly, goes hand in hand with a player's success.

According to Kagiso Rabada, Gerald Coetzee has the potential to be a 'South African great' Getty Images

"Passion is important," Rabada says, "because you know, there are so many distractions around you that can inhibit your talent to come through.

"It can also put a mental block on you, that's when you start to lose yourself a little bit. When you can channel your energy and channel your focus, that's when your potential and talent has the best chance of expressing itself."

As the Under-19 World Cup nears its knockout stages, which begin on Tuesday, Rabada said this was the time for future stars to step their game up.

"In do-or-dies, you need to be more street smart, more adaptable," he said. "Knockouts force you to make a play on the spot. Even though it's very hard to treat it like a normal cricket game, you need to think of it that way because you then have a clear focus.

"If you make a play under pressure, that means way more than doing it under regular circumstances. For me, it means way more to perform under pressure. All those cricketers who are regarded as greats always performed when the pressure was high.

"[The 2014 U-19 World Cup semifinal win] was so important because it forced me to perform under pressure. It challenged me in that sort of environment, against a good opponent."

Rabada picked out a few South Africa players who could go on to the represent the senior side very soon. However, he said that for them to bloom, they need to be handled with care.

"I've played with Gerald Coetzee in the Mzansi Super League," Rabada said. "The guy can already bowl at 145-plus and he's 19, so he's an extraordinary talent. He needs to be managed well and can be a South African great if he keeps doing what he's doing. Then there's the captain Bryce Parsons. Jonathan Bird looks good too. The talent is there within this team, they just need to be managed better."