Unless injury or illness intervene, India will have five certain starters on Boxing Day at Centurion - KL Rahul, Mayank Agarwal, Virat Kohli, Rishabh Pant and Jasprit Bumrah - and three near-certainties - Cheteshwar Pujara, R Ashwin and Mohammed Shami. Picking the rest of their XI, however, could be a difficult task. Here are three major questions that India will potentially ponder over in the lead-up to Boxing Day.
Five bowlers or four?
India have played 15 Tests since Boxing Day last year, and each of the XIs have included five bowlers, with either Ravindra Jadeja or Washington Sundar slotting in as a batting-weighted allrounder in 13 of them. Neither is part of the squad in South Africa, which could make a five-bowler combination tricky to balance.
R Ashwin, however, has been a rejuvenated lower-order force this year. Having gone through a prolonged dip - he averaged only 16.72 from the start of 2017 to the end of 2020, with one fifty in 39 innings - he has lifted his batting back to a level near its best. He averages 28.08 in 2021, and apart from his century against England in Chennai, he's made a few other useful contributions too. There was the unbeaten, 190-minute match-saving effort with a bad back in Sydney, of course, but also a series of valuable knocks against New Zealand - a 27-ball 22 in the World Test Championship final when Kyle Jamieson was running riot, and a pair of thirties full of crisp off-side strokes in Kanpur.
India, therefore, could pick five bowlers if they feel Ashwin and Shardul Thakur - who has three fifties in four Tests - can provide enough with the bat at Nos. 7 and 8 to make up for the lack of batting ability among their Nos. 9, 10 and 11.
Rahane, Vihari and Iyer
The debate between Hanuma Vihari and Shreyas Iyer is covered in greater depth here, and both make strong cases for selection.
Ajinkya Rahane, meanwhile, averages 19.57 in 12 Tests since scoring 112 and 27* in India's victory at the MCG last year. He contributed a vital third-innings 61 to India's win at Lord's in August, but since then, six visits to the crease have brought him scores of 18, 10, 14, 0, 35 and 4.
Rahane wasn't going through anywhere near as lean a patch in the build-up to India's tour of South Africa in 2017-18, but they still left him out in the first two Tests. If Kohli and the new coaching staff are inclined to make such a decision this time, India could play either Vihari or Iyer at No. 5, Rishabh Pant at No. 6, and five bowlers, or play both Vihari and Iyer at Nos. 5 and 6.
Ishant vs Siraj
New Zealand's greater depth of pace resources was a key factor in their victory over India in the World Test Championship in Southampton. Having picked three quicks and two spinners in that game, India switched to a 4-1 combination for the rest of their tour of England, leaving Ashwin out of four successive Tests.
If the conditions demand it, India have two routes to playing a 4-1 combination - they could pick Thakur and three other quicks, or simply pick four outright fast bowlers who offer very little with the bat. One other option, if conditions are heavily loaded in favour of seam, would be to pick four fast bowlers and no spinner.
A 3-1 attack could also be on the cards, if India feel the need for the security of an extra batter.
In all these cases, the competition for the fast-bowling slots will be fierce. Bumrah is an automatic pick, and Shami probably is too, and both will be raring to go after being rested for the home Tests against New Zealand.
Ishant Sharma, however, is an interesting case: he has world-class numbers since the start of 2018 - with 85 wickets at 21.37 in 26 Tests - but his numbers this year haven't been too strong - 14 wickets in eight Tests at 32.71. His five wickets were key to India's victory at Lord's, but he looked completely off the boil in the next Test at Headingley, and less than threatening during the Kanpur Test against New Zealand. Two wicketless Tests cannot undo the work of a 311-wicket career, but India will probably keep a close eye on his rhythm in the nets leading up to December 26.
There is, of course, a bigger reason for Ishant's place potentially being under threat than his own rhythm or lack thereof. In the space of just 10 Tests, Mohammed Siraj has made a strong case to be part of India's first-choice pace attack, and his three-wicket new-ball burst against New Zealand in Mumbai showcased everything that makes him so dangerous: slippery pace, a line that denies batters easy leaves, movement off the deck, and a sharp, accurate bouncer.
Do India go with Ishant's experience and ability to bowl dry, or Siraj's all-out aggression?