Excited by our new-ball combination - du Plessis

Kagiso Rabada and Lungi Ngidi share a light moment AFP

They have only little more than a quarter of the number of caps of South Africa's most lauded new-ball pair, Dale Steyn and Morne Morkel, but Kagiso Rabada and Lungi Ngidi have made captain Faf du Plessis "really excited" ahead of the 2019 World Cup. While Steyn, who has 116 caps, remains in contention for the tournament, Morkel, who played 117 matches, has retired. But du Plessis has seen enough of Rabada and Ngidi in the 59 matches they've played between them to believe the future is in good hands.

"I'm really excited about our new-ball combination of Kagiso and Lungi. They're strike bowlers, they get early wickets," du Plessis said, on his return from Sri Lanka on Friday.

While Rabada's pedigree has been on display since his 6 for 16 on ODI debut more than three years ago, Ngidi has properly announced himself in the current series. With four of the five matches played, Ngidi's leads the wicket-takers' charts, with 10 scalps at 20.10, and his combination of pace and control should make him a shoe-in for next year's show-piece.

But du Plessis was careful not to rule Steyn, who has been vocal in the media about his desire to play at the World Cup, out of contention despite his focus on red-ball cricket at international level since his spate of injuries. Du Plessis even included another experienced name, Vernon Philander, in the mix, although Philander has not played an ODI in three years. "Of course, Dale and Vern are in the frame," du Plessis said. "Anyone can still put their name on that list, there's still plenty of time."

Earlier this year, coach Ottis Gibson also indicated Steyn and Philander could be considered for the tournament. But Gibson said, if they were to play, it would only be in the last 10 ODIs before the tournament (which are against Pakistan and Sri Lanka at home) so South Africa could experiment beforehand. Du Plessis reiterated that sentiment now. "The senior guys don't need any more experience, it's about trying to help the younger guys gain as much experience a possible," he said.

To that end, South Africa's pace attack in Sri Lanka on this tour have a combined total of 94 caps - without Rabada's 51, the remaining four bowlers have only 43 matches between them. Of those, Andile Phehlukwayo has had the most match time, with 29 caps, and his experience shows. After a poor first game, Phehlukwayo has performed well with a wily display of cutters.

The other half of the squad - the batsmen - still rely on their old-timers, with du Plessis, Hashim Amla, David Miller and JP Duminy forming the spine of the line-up. Duminy leads the run-charts and appears re-energised following his retirement from Test cricket last year and he could have a big job to do at the World Cup. "The biggest shift I've seen is in the real discussions we've had on where his head needs to be and he's in a really good space," du Plessis said. "The decisions he's making, especially when batting, are positive. It fits in with the fearless brand of cricket we want to play. He's been exceptional in this series."

Amla has re-found form after a lean run in Tests and has started to "free up and play the type of Hash innings we're used to", and Quinton de Kock has been promoted to a senior, along with the additional role of stand-in captain. While du Plessis could not confirm whether de Kock's elevation is part of the succession plan, he said it was intended to help de Kock develop. "We certainly felt that when Graeme (Smith) left the team, there were limited opportunities for the young players to learn, to get one or two occasions to captain a bit and few young guys with leadership capabilities. For a guy like Quinton, I feel he'll grow a lot just by getting a bit of extra responsibility. As a player, it's easy just to focus on your own game and when you're captain, you don't have that luxury. This will teach him a different side of game. It's a nice opportunity to learn a few new tricks about himself."

But, ultimately, Aiden Markram's name continues to crop up as someone to whom leadership "comes more naturally" and now du Plessis hopes he can find the confidence to come out of his first patch of poor international form. "For a young guy going through a tough time I can see he's got a very mature head on his shoulders. He's understanding that it's part of cricket, going through the up and downs, that good times can be followed by bad ones. The conversations have been that you don't become a bad player overnight. He's really excited about having to try and figure out what he needs to do to become an even better player."

Markram will continue to get opportunities high up in the batting order but knows that others, like Reeza Hendricks who scored a century on debut, are also around. That could make World Cup selection a problem of plenty, something du Plessis will be more than happy to have. "We've got some nice young batters coming through as well, putting some pressure on the others. Obviously with AB (de Villiers) leaving, we're playing with ideas on what might be the best line-up but there's still enough time to answer a few unanswered questions."