Kagiso Rabada is 22 years old. He has been playing Test cricket for almost two years and on Friday will start his 22nd Test as the leader of South Africa's pack, whether he likes it or not.

Rabada has repeatedly shied away from being called a spearhead but this time he will have to shoulder the responsibility. For the first time January 2007, South Africa will go into a Test without one of Dale Steyn, Morne Morkel and Vernon Philander. Though they have been sans Steyn for almost a year, have been without Philander and Morkel for long periods in the past, and Faf du Plessis hopes the 'big three' will still play for "three or four more years," this marks the start of the changing of the guard.

Du Plessis preferred to look at it as a talent search and was relieved that it was coming in this series, against Bangladesh. "With the big players missing, especially against teams like Bangladesh, it's really important to see what your resources are," he said.

"We are very unlucky that we have four bowlers at the same time that are injured. You are never really faced with a scenario like this. But for the first time I am getting to see somebody like Dane Paterson with the red ball in his hand and see what he is capable of. That's good for our country to see who else is out there. If we were so unfortunate again that we had four seamers injured then, we will have a really good idea. It's important in a series like this that you can see who else is out there because we know what we have in that top four."

The fourth injured bowler is Chris Morris, who has only played four Tests. That South Africa regard him highly enough to put him in the same bracket as the other three quicks speaks to the concerns around the depth of the domestic system.

A brief scan of the scene does not throw up any obvious names pushing for Test places. Even Paterson, who was included in this squad, was something of an outside pick considering he finished the last first-class season in 13th place, with 23 wickets at 29.04 and has taken 13 wickets in first-class cricket at 31.76 for South Africa A. The likes of Beuran Hendricks, Dwaine Pretorius and Junior Dala have been mentioned but, largely, it seems South Africa will stick to the same bowlers they have been using in the past, and hope they will become world-beaters.

In Duanne Olivier, they have someone with potential. He tore up the first-class competition last summer with 52 wickets at 18.13, a remarkable feat in itself made even remarkable by the fact that plays most of his cricket on a fairly flat Bloemfontein surface. But in four Tests so far, Olivier has struggled with rhythm and consistency. He may get the chance to improve on that in the second Test, especially if he takes the new ball, which du Plessis hinted was a possibility. "It's a nice responsibility for Duanne. He probably prefers to have that new ball is in hand," du Plessis said. "Every bowler is a confidence bowler so if he gets that confidence and he gets he's tail up. I reckon he will click and it will be really good to see him go."

And then there is Wayne Parnell. Much like JP Duminy, Parnell is in danger of failing to fulfill his potential. His injury record is much better than his cricketing one and he has only played five Tests since making his debut in 2010, but South Africa seem determined to turn him into a regular. Parnell was included in the squad despite not playing four-day cricket since April and after being withdrawn from the first-class opener. Du Plessis is hopeful he is ready to play; the South Africans could be forgiven for wondering how long he will stay ready. "I don't know from a workload point of view but from how he looks, he looks ready and fit," du Plessis said.

As for the mounting injuries, du Plessis doesn't have much of a clue about their cause apart from the obvious. "Age is a factor. Dale, Morne, Vernon are all getting to that stage when your body has a few more niggles," he said.

But he hopes the younger crop will take note that there is something they can do to manage themselves when the niggles start. "It becomes more important that you work harder. Morne is a great example of that," du Plessis said." He had a really bad back injury and the work he did behind the scenes for a year was a great example for the young guys. He came back and he was at his best ever. Myself included as a batsman. I don't rock up to the field anymore and just get going. I need a about a 40-minute stretch. It's part of getting a little older. Our bowlers need to understand that they need to possibly do a it bit more than they are used to because when you've bowled all those overs in your career, it will catch up to you."

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Mushfiqur Rahim is 30 years old. He has been playing Test cricket for 12 years and on Friday will start his 58th Test, and 34th as captain. He is the leader of Bangladesh, whether he likes it or not.

Under him, Bangladesh have become a dangerous team at home and want to become competitive abroad. But they need to be able to bat strongly if they want to stand up to an attack like South Africa's in conditions which will challenge them. Rather than relying on rookies, Bangladesh need their senior players to step up. In the line-up, that would be Mushfiqur, Mominul Haque and Mahmudullah.

They are the only three Bangladesh players to have played a Test without Shakib Al Hasan or Tamim Iqbal, back in March 2013. Then, a double-hundred from Mushfiqur was the main reason Bangladesh saved the game. Mominul was making his debut, and scored 55 in the first innings. Mahmudullah was out for a duck but took 3 for 70 in the second innings. Imrul Kayes is the only other player in the side to have played more than 20 Tests but with an average of 26.31, he has a lot of work to do, which may only make the absence of Shakib and Tamim more glaring.

"It is a major setback to not have your two best players," Mushfiqur said."We really needed them here. We lost the first game badly. But time doesn't stand still for anyone. Injuries are not in our control. The batsmen have to take advantage of good starts and put together big partnerships; the bowlers have to bowl in good line and length and consistently put them under pressure. The last time we missed them was in Galle. It wasn't an easy game for us. Sri Lanka was a far better team at that time."

That Sri Lankan side included Tillakaratne Dilshan and Kumar Sangakkara; it had Nuwan Kulasekera and Ajantha Mendis in the attack and though the Galle pitch was flat, Bangladesh had to go where they had never gone before to top 600.

They don't need to think about anything that big in South Africa. Not yet. Instead, they want to concentrate on heeding the "warning," their second innings gave them in Potchefstroom when they fell away on the final morning. "Our batting unit collapsed in a big way in the second innings," Mushfiqur said. "I haven't seen one of such a scale in recent years. It was a warning for us."

He wants to see his men take more responsibility, starting with the openers and running through the middle order, as Bangladesh search for boldness on the road. "I have a lot of confidence in them Soumya and Imrul to return among the runs. They can take a step forward if they can score runs in this game, particularly in the absence of Tamim,"Mushfiqur said. "I think this is an opportunity for the others in the squad. I want them to make use of this opportunity."

Firdose Moonda is ESPNcricinfo's South Africa correspondent