Why India have made the ball reverse, and NZ haven't

You are a fast bowler visiting India, you want to do your bit before the spinners take over, you want to take early wickets or at least make sure to keep the batsmen quiet. Your team loses the toss, you run in with a hard new ball, you let it go as fast as possible, it pitches, loses all of its pace and bounces knee high. It can be a disheartening sight.

So you need an equaliser. You need reverse swing. Dale Steyn had it in Nagpur 2010. James Anderson had it in Kolkata 2012. For New Zealand of 2016, though, this equaliser has been missing.

India have lost six wickets in an innings three times this series, yet they managed a further 57, 116 and 157 runs. New Zealand's corresponding additions - 7, 42, 82 and 41 - tell you where this series has been won and lost. India have spinners who can run through tails. New Zealand don't. India have a lower order full of capable batsmen, more importantly batsmen who are experienced in these conditions. New Zealand don't. This is where the equaliser would have helped.

These are some of the earliest Tests in an Indian home season. With climate change resulting in prolonged summers, they have been played in oppressively hot conditions. The first two Tests were in cities on the banks of the river Ganga, which adds to the already potent humidity. Though New Zealand's bowlers are capable of reverse swing, when you are sweating so much, it is nigh impossible to pull off.

This leads to the obvious question - why have India been able to reverse the ball? The fact is they almost haven't. On the three occasions they did get reverse swing, it was right after a ball change.

In the first innings of the Kolkata Test, New Zealand asked for the ball to be changed in the 54th over but they were denied. This was during the big partnership between Ajinkya Rahane and Cheteshwar Pujara. When India bowled they showed the ball to the umpires as early as the 10th over. It was finally changed in the 47th, and as he did in the second innings in Kanpur, Mohammed Shami began reversing it and had BJ Watling lbw.

Changing the ball is a matter of luck and when you get one that is dry and semi-new, it is easier to work on it and make it reverse. New Zealand have not been able to get the ball changed at all in the series. Without suggesting anything untoward, New Zealand coach Mike Hesson told ESPNcricinfo before the start of the Kolkata Test that this had been a factor.

"It's very difficult for both the sides to keep the ball dry when you are soaking wet," Hesson said. "And that makes it difficult. Hence, when you are able to get the ball changed, when the ball is dry to start off with, it's easier to get it to reverse quicker. That's something that sides will look to do."

Rohit Sharma also spoke of the importance of the ball change during the Kolkata Test. At the end of the third day, he was asked about how difficult it had been to reverse the ball. His first reaction was to point to the ball change, but he stopped himself. "I don't think so it was difficult [to maintain the ball]," Rohit said. "Once the ball got changed… I think Shami was bowling this morning... I think… When they changed the ball, you know…

After lapsing into a pause, Rohit went on to explain why reverse swing was scarce and what India were doing to make it happen. "When you are fielding in such humid conditions your clothes are wet all the time, so you make sure that one side of the ball is dry all the time. It's pretty difficult but we have identified a couple of guys in our team who have to make sure that they keep their pants dry all the time to shine the ball. It is happening, so we have got certain things going in our team, which is good. The first session when we were bowling with that ball there wasn't much reverse swing, like we saw in Kanpur, because of the surface and the outfield, it's lush green outfield. There wasn't much reverse swing, and you might not see so much of reverse swing that we saw in Kanpur."

India managed to reverse the ball in the second innings without a ball change too. It began as a mysterious art, but a lot about reverse swing is known to all the teams now. Still, like many things cricket, it depends on a bit of a good luck. For India the ball had been damaged enough to merit a change, for New Zealand it hadn't. And when you get a drier ball, the reverse swing still has to be executed. Shami has done so.

Trent Boult and Neil Wagner or Matt Henry will hope a couple of players on their team can keep their pants dry all the time. Or that it is not as humid in Indore, and if it is that at least they get a drier semi-new ball so they can get the opportunity Shami has had and has exploited wonderfully.