Hashim Amla is unique in many ways - his backlift, his beard, his batting records - and he could soon find himself the holder of another individual milestone. Test captain Faf du Plessis said there is a chance no other South African will follow in Amla's footsteps and play in 100 Tests.

"I am going to make a big call and say Hash (Amla) is probably going to be the last guy that plays 100 Tests for South Africa because of the way that the game is changing," du Plessis said. "Quinnie (de Kock) and KG (Rabada) are possibly looking at that as youngsters but it's a long way into the future."

Du Plessis is not being overly dramatic in that assessment. The average age of South Africa's 13-man squad is 27.85, including two 24-year-olds who are yet to play a Test: Theunis de Bruyn and Duanne Olivier. Take them out and the average age of the expected playing XI at the Wanderers, with Wayne Parnell being swapped for Kyle Abbott, is 28.54.

Of those, five players: du Plessis, Amla, Stephen Cook, JP Duminy and Vernon Philander are over 30. Dean Elgar is 29. De Kock and Rabada, who are 23 and 21 respectively, are expected to have lengthy careers but du Plessis said that does not necessarily mean a large collection of Test caps.

"It's a massive call to make. Test cricket these days, the game has evolved so much. If you look at Hashim and AB (de Villiers) and Jacques (Kallis) and Graeme (Smith) and all those guys, it was a period of a lot of Test cricket that was played over a long period of time. Now, there's lots of T20s, so I think the game is changing a little bit, that you won't play for as long because there is so much more cricket," du Plessis said. "What I mean by that, is that its really special for Hash to do something like that. I'm not going to get to 100. The guys in the team that are playing now, JP, all those guys, its something we will never get to."

Du Plessis had forgotten the one man closest to Amla, Dale Steyn. He has 85 Test caps but is not expected to return to action until June as he recovers form a shoulder injury. Steyn told ESPNcricinfo he thinks it could take him as long as three years to reach 100 Tests but after watching tribute videos to Amla on television in the lead-up to the Wanderers Test, he is motivated to get there. Perhaps any player would be, because as du Plessis said it is an "amazing, amazing effort".

It's also a time to celebrate what a player has done over a sustained period of time and although Amla has stayed out of the limelight, attention has found him. His team-mates have heaped praise on him, with du Plessis the latest to join the chorus.

For du Plessis, Amla has been an example of consistency, not just in runs but in attitude. "He has been the rock of our batting. He has been the most consistent player I reckon with Jacques Kallis that South Africa have ever had," he said. "Of course he is not scoring as much runs now but what he brings off the field still offers a lot. Hashim when he is scoring runs or when he is not scoring runs is exactly the same person and that brings a calmness to the dressing room. Even when he is not scoring runs, he is offering a lot of value and for me as a player, I've learned a lot from that. You need to look at success and failure in exactly the same way."

Although Amla is no longer captain, he continues to offer leadership which is of particular importance to du Plessis, who has just taken over. "As a leader he's a huge asset to me - I rely on his knowledge a lot. Take away the runs, the demeanour and person he is in the dressing room is very calm. Even if he goes to the wicket and doesn't score runs it feels like he relaxes the batting unit - he's just got that personality," du Plessis said.

Du Plessis would like the rest of the line-up to learn how to bat big, like Amla. Not only is Amla the holder of South Africa's highest individual Test score but he also has the second-most number of double hundreds behind Smith, and his conversion rate is something du Plessis wants the team to try and emulate.

"Hash's concentration - that's his biggest thing and his biggest asset. It's something that I admire and it's something that I challenge myself and the other batters with," du Plessis said. "It's happening too often these days that you don't get enough guys to anchor big and score big runs. To score hundreds is great - we want to score hundreds - but to push ourselves to get even better to get to 150s and 200s. Hash is normally a guy that leads that."

While Amla will be celebrated at the Wanderers, there will be also be questions about his future. After 100 Tests and at his age, 33, there are people wondering whether Amla will retire in the near future. Du Plessis brought news that for now, they can shelve that thought.

"I've spoken to him and he's still very keen to push it as long as that great body of his will let him go. But he's not even thinking about retirement."

Firdose Moonda is ESPNcricinfo's South Africa correspondent