Let's say all goes to plan. India win the Melbourne Test, the Border-Gavaskar Trophy stays with them, they travel to Sydney to try to preserve their lead, and R Ashwin is fit. Who will India pick then? Ravindra Jadeja, who has bowled 57 overs for 127 runs and five wickets in Melbourne, or Ashwin, who bowled 86.5 overs for 149 runs and six wickets in Adelaide?

Of course, the conditions will decide whether they can play both of them. If the Sydney pitch is true to character, and there has not been much rain in the lead-up, there's a good chance both of them might play if they are fit, with Hardik Pandya possibly slotting in as the third seamer. But there will be a big decision to make if either the pitch is not dry or Pandya, coming off a back injury, is not ready for Test cricket yet. This is where some of Jadeja's history comes in first.

Between Southampton 2014 and Melbourne this year, he didn't play a single live rubber as the lone spinner. When India went in with two at Lord's, Kuldeep Yadav was picked ahead of Jadeja. Unless there have been other fitness issues, which were not disclosed as with the time in Perth, there has been clear lack of faith in him.

One of the reasons for that lack of trust could be the number of left-hand batsmen India have played against. England and Australia both have a good amount of them, which makes Jadeja a less potent threat, according to conventional wisdom. But as he showed in this Test, when Jadeja can latch on to a spot of rough, that conventional wisdom doesn't always hold true. This is also what happens when India's right-hand batsmen find themselves in the headlights with opposition offspinners. And with sides bowling more right-arm seamers, in theory left-hand batsmen should have more rough to contend with than the right-hand ones.

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The one problem with that is left-hand batsmen grow up facing this all the time, so they are more adept at handling a left-arm spinner hammering that rough than offspinners landing it in the rough outside a right-hand batsman's off stump. Moreover, the rough created by a left-arm fast bowler is more prominent and pronounced than the one created by various right-arm quicks. A conflict exists in theory as does on the field. In pockets, Jadeja seemed unplayable to left-hand batsmen, drawing short-leg catches from Usman Khawaja and Marcus Harris. And yet, in this Test, he averaged 42 against left-hand batsmen and 15 against the right-hand ones, also maintaining a better economy rate against the right-hand batsmen.

By no means can Jadeja's contribution to what should be a memorable win be understated. He has bowled a major share of the overs, keeping the run-rate down, making sure the fast bowlers remained fresh, and has himself contributed five wickets, more than 25% of those fallen.

"Jadeja has matured a lot over the years," India's bowling coach Bharat Arun said. "What he has done in the last one-two years, he has gained a lot of confidence and the way he has progressed today and also the way he did in England at The Oval, we can be quite confident that Jadeja can lead the spin attack.

"I would say that a spinner maturing is about him understanding and discovering himself. And how he does it is he tries various angles with which he can bowl and variations in position of wrists. In the last couple of years, Jadeja has learnt quite a lot and that has helped him evolve from what he was earlier."

Ravindra Jadeja is overjoyed after taking a wicket Getty Images

Jadeja's fielding might give him an edge over Ashwin, but he loses it right back when it comes to batting on bouncier tracks. This is where Ashwin's other quality comes in. If Jadeja is good at hitting the rough over and over again, Ashwin has the subtleties to beat batsmen in the air, those small changes in pace and trajectory that Harris acknowledged in Adelaide. It is when nothing was happening for him that Jadeja began to fire the ball in on the fourth day. Tim Paine's wicket was a bonus when Jadeja went over the wicket and the batsman went to cut. Who can draw a genuine error when nothing is happening is a question India's think tank will ponder. Kuldeep Yadav remains unlikely to play if it is deemed only one spinner is required; playing him as a lone spinner is a big risk because he can go for runs and you can't afford one of the four bowlers to be unusable.

If India go to Sydney with a series lead in hand - which should be a mere formality - it could come down to their lead spinner to preserve that lead, which will make this selection between Jadeja and Ashwin important. However, with his performance in Melbourne, Jadeja has done enough to earn the team management's trust should Ashwin not recover in time.