Be careful what you wish for, South Africa. It may just come true.

At the start of this series, selection convenor Linda Zondi made a strident case for South Africa using these limited-overs matches, and possibly the ones in Sri Lanka later the year, to cast their net as wide as possible, and experiment with different combinations ahead of the 2019 World Cup. Now, that's what South Africa have been forced to do after a third frontline player was ruled out of the ongoing series against India.

Quinton de Kock will spend between two and four weeks recovering from a wrist injury and joins captain Faf du Plessis on the list of those in a race against time to be fit for the four-Test series against Australia, which starts on March 1.

Du Plessis has a broken finger and needs between three and six weeks to recover. The other injured member is AB de Villiers, who also has a finger injury, and is expected to be back by the end of the week. His finger problem only needed up to two weeks to heal. Curiously, though, de Villiers was spotted playing a round of golf the day after he was ruled out of the first three ODIs.

De Villiers' return may be rushed given the spate of injuries that have hit the South African squad. It's not just that du Plessis and de Kock are out, it's that the captain and the wicketkeeper-opener are out. The two certainties on any team sheet have disappeared, forcing South Africa to dig into their depth, just as they wanted to, but perhaps not in these circumstances.

Though du Plessis has conceded that the forward-thinking of "Vision 2019" may come at the expense of immediate results, he was probably not expecting the cost would be so great. South Africa trail 2-0 in the six-match series, and have lost 13 of their 18 wickets to wristspin. Nevermind 2019, they have to start turning things around now if they are to stay in the series and give themselves a proper opportunity to assess anything other than ghosts against spin.

Theoretically, having injuries should provide the chance to test the fringe players.

Everyone already knows de Villiers' ability against any kind of bowling. Du Plessis, apart from being the captain, is the only South African batsman to score more than 37, and he scored many more. His century in Durban saved South Africa from a defeat like the one they suffered at Centurion.

What South Africa don't know is whether there is anyone else in the middle order who can come close to replicating them.

JP Duminy must be on his last legs after prolonged periods of under-performance in all formats. He has retired from Tests, but if he does not start contributing as reliably as a senior player should in ODIs, South Africa could look elsewhere for 2019. And elsewhere may be no further than Farhaan Behardien and Khaya Zondo.

Behardien was puzzlingly left out of the squad despite being one of the most consistent players in the domestic one-day competition, but was drafted in when du Plessis was injured. He didn't play on his home ground, SuperSport Park, because Zondo debuted. Though the batting failed miserably, Zondo didn't. He only scored 25 but he managed to stay fairly calm when the team slumped to 51 for 4. He needs more chances. Behardien, though, arguably needs them first.

Despite widespread public criticism for not doing enough in general, Behardien is a reliable finisher who often drew the short straw when it came to opportunity in ODIs. Either he had very little time to bat, or had only the tail to bat with. His confidence was beaten, and being dropped would only have hurt it more. But South Africa should trial him properly in the remaining four games and see if he has the stuff to take them to 2019.

David Miller and Chris Morris have been identified as keepers but both need to perform better than they have so far. Their reputation buys them some rope but they must not use it to hang themselves. And then there is Aiden Markram. Thrust into the captaincy and the No. 3 position, Markram will probably be forgiven if he fails. But if he passes, South Africa could find a missing piece.

In de Kock's absence, Markram may even open the batting, which would suit him better, and create another middle-order opportunity. Heinrich Klaasen is certain to play, at least at Newlands, because de Villiers remains unavailable. Klaasen has been on the radar for almost a year - he travelled to New Zealand as the back-up wicketkeeper for the Test series in March last year - and he is in good form, having finished the one-day cup as the third-highest run-scorer.

Importantly, he also presents the first real challenge to de Kock, who may have been saved from being dropped by getting injured. De Kock has not made a significant score since his century against Bangladesh in an ODI last October. Since then, he had a lean domestic twenty-over competition and a tough four Tests. His problems against spin have been exacerbated by an overall uncertainty in his own game. In the first ODI, when he was given out lbw after missing a flick, he did not even consider a review but if he had, he would have been not out. His head just does not seem in the game.

Out loud, du Plessis and coach Ottis Gibson have touted the familiar line about de Kock being "that kind of player." They've given him leeway as someone that doesn't think too hard and should not have too much pressure put on him because they trust he will just click. In some circles, there are concerns that de Kock's routine when he is not part of the team camp are not rigorous enough for an athlete of his stature.

What it may take for de Kock to realise that is to see that there is someone else. South Africa have dropped de Kock before - he didn't play the Tests in India at the end of 2015 after a patch of poor form. He was rested for T20Is, when Mangaliso Mosehle was brought in, but de Kock was establishing a firm hold over the wicketkeeping position, like Mark Boucher.

Boucher spent a decade-and-a-half in the Test side, for all but four matches when he was replaced by Thami Tsolekile, through good form and bad. When he retired, South Africa did not really have a plan. De Kock is far from that, but South Africa can't make the mistake. Affording Klaasen, and maybe even a few others, an opportunity is the best thing to keep de Kock on his toes.

Any healthy sporting set-up has competitiveness, even if it takes time to find it. Over the last two summers, South Africa have had to unearth it among their bowlers as all of Dale Steyn, Vernon Philander and Morne Morkel were sidelined. Now, they have to do it for the batsmen and the wicketkeeper.

This is what you wished for, South Africa. Now work it out.