England now lead the series 2-1. © AFP

It's amazing what a couple of good wins and the emergence of something resembling a coherent plan can do to the atmosphere surrounding a team. In the space of just a couple of weeks, England have gone from a winter verging on calamitous to a sort of heady, if realistic, optimism about the development of the Test side. The swift turnaround has been achieved thanks to two excellent performances in Cape Town and Port Elizabeth and bolstered by the quality and experience of the players who have not been involved. This is an England side thrown together. And yet they have still been able to win.

In Port Elizabeth, England were missing James Anderson, Jofra Archer, Rory Burns and Jack Leach because of injury. Archer, Burns and Leach missed the victory in Cape Town, too. At the start of the series, all four would have been in England's strongest team. Although fully fit, Jonny Bairstow and Chris Woakes have not yet been selected either, two experienced players who have done some wonderful things in Test cricket. Before this tour, there wouldn't have been many people willing to bet on England being on the verge of a series victory with all those players playing bit parts.

The likes of Ollie Pope, Dom Bess and Dom Sibley have stepped into the breach, however. Their strong performances have created the most competition the Test squad has had since Joe Root took over as captain in 2017. And as every captain worth their salt will tell you, having strength in depth is the sort of difficult problem they want. Better to have too many good options than not enough. While England are far from the finished article, they certainly have a bigger pool of players to pick from now.

Some of the opportunities given to players in this series have been forced on England. Injury to Burns meant Zak Crawley got a chance at the top of the order and he showed promise in Port Elizabeth. Leach's failure to recover from illness meant Bess got a chance, one he has taken. Others have been selected above more established players. Pope has kept Bairstow out of the side, for instance, while Sam Curran has been preferred ahead of Woakes. How they have come together is largely immaterial. Come together they have and it's worked out pretty well so far.

England will hope these young players continue to impress. If they do, selection headaches will follow. One might materialise this week if Archer recovers from an elbow injury in time for the final Test at the Wanderers on Friday (January 24). If he does, how will Root and head coach Chris Silverwood fit him in?

Should they leave Dom Bess out, despite his maiden five-wicket haul at St George's Park, and pick an all-out pace attack on a pitch expected to suit fast-bowling? Or do they swap Archer for Sam Curran, a bowler averaging 29 with the ball in the series? Will Mark Wood's body hold up to back-to-back Tests or will they want to unleash both of their quickest bowlers on South Africa? It's not a straightforward choice.

"We've got a couple of sessions coming up so Jofra will bowl then and if he's fit that's another great headache isn't it?" said Silverwood. "I've got to find a way that potentially he comes back in and at the same time we've got Woakesy sat there as well. He's been bowling beautifully. So we've got options available to us that is again superb. Jofra today felt good so hopefully he's going the right way.

"You look at the bench we've got, they're working incredibly hard and there's so much talent there and so much experience. We need that as well. We talk about the youngsters a lot but we need the experience dotted in amongst it as well so they can learn by getting it right rather than making mistakes all the time."

Not that England's young players have made too many mistakes in the last two Tests, of course. "It's always great to see the youngsters come in and achieve as they are doing," Silverwood said. "Day after day one of them is always putting his hands up and making a difference in a game for us. It's fantastic and over a period of time they will become Joe's team. All of them have a great attitude and a lot of talent, which always helps.

"The innings Ollie Pope played in the Test was very grown up for such a young lad and I mean that in a good way. He was composed, he read the situation well and applied himself unbelievably. He's got his feet on the ground as well; he works incredibly hard, as all the guys do in that dressing room so that puts him in a great place. They are all good characters, so I'm not surprised they've done well.

"If you take Dom Bess, for example. He's been away on a spin camp, worked hard, has come here, impressed in the nets and when given the opportunity he's taken it, which is exactly what you want."

The only player who has yet to make a telling contribution is wicket-keeper Jos Buttler who is averaging 17.40 across the three Tests and only 22 since the start of last summer's Ashes. With Bairstow and Ben Foakes as high-class competition, Buttler could do with a score in Johannesburg to quell any speculation about his place. "It's a team game and he will come good at some point," said Silverwood. "He's going to hurt someone. We know that."

Buttler will have a better chance of showing what he can do if England's top order can continue providing a platform for the more fluent players at numbers four to seven. Sibley, Zak Crawley and Joe Denly did that in Port Elizabeth, batting for more than 300 balls combined, to blunt South Africa's new ball attack. That then allowed Pope and Ben Stokes to make hay on day two, propelling England on to their biggest first innings score since the 514-8 declared they managed against West Indies at Edgbaston in August 2017.

"We pick a team that will try and get us big first-innings runs and the top three have laid some fantastic foundations time and time again for us to go on and get the big scores," said Silverwood. "We're learning to do that now. As I've said before we're not the finished article by a long way but for them to go out and do it in this game and win will give them a heap of confidence. The team is picked to get us where we want to go."

Right now, England are only on the start of an upward curve. As Root said after the third Test victory, where they want to get to is to be the best side in the world. That is still a long way off yet. But the optimism generated over the last few weeks is real and justified. And part of the optimism comes from the players England have been missing. Winning with a side full of established players is one thing. Winning with a team with so much youth and so much inexperience is quite another.