If, at the start of 2022, you were asked which wristspinner among Yuzvendra Chahal and Kuldeep Yadav was going to be picked for the ODI World Cup the following year, you would not be blamed for choosing the former. In fact, that would be the sound, educated guess.

After all, from the end of the 2019 World Cup to the end of 2021, Chahal had picked 34 wickets in 21 ODIs at an average of 28.47. Kuldeep, in that same period, played a game more, got just 26 wickets, and averaged 43.73.

Nothing seemed to be going right for Kuldeep around then – he was even relegated to the bench by his then IPL franchise Kolkata Knight Riders.

But then, something changed.

It’s not like Chahal did a lot wrong. He picked up 24 wickets in 16 ODIs between the start of 2022 to now, and his average improved marginally to 27.91. Even his economy rate dropped from 5.70 to 5.53.

But Kuldeep’s transformation was massive.

Suddenly, he was bowling quicker, but still getting the turn that troubled batters when he first burst on to the scene. His variations were still as effective, if not more, and now came with more zip off the surface.

The results followed.

From the start of 2022, Kuldeep has picked up 43 wickets in 24 matches and his bowling average has shot down to 18.93 (in this period). His economy rate, which was 5.76 between the end of the 2019 World Cup and the end of 2021, dropped to 4.70. He has picked up three-wicket hauls against Australia and New Zealand and four-fors against South Africa and Sri Lanka. And then, of course, there was the 5 for 25 against Pakistan in the Asia Cup Super Four game.

A criticism Kuldeep often faced when his career seemed to be all downhill was that he was bowling too slow. Despite the prodigious turn he would generate.

But the solution wasn’t simple, because Kuldeep had to get quicker without losing the trajectory that so deceived the batters, and turn that made him so good in the first place.

A knee injury, suffered during IPL 2021, turned out to be the point the transformation started. The surgery that followed offered him a chance to start over, in a sense. As he completed a five-month recovery and got back to bowling, he tweaked his run-up from what was almost a 45-degree angle to a much straighter approach. That was change number one.

“It’s been over one-and-a-half years since I had surgery,” Kuldeep said after his heroics against Pakistan at the Asia Cup. “The run-up has become straighter. The rhythm has become aggressive. The approach is nice.”

Other things might have changed too.

“Maybe my hand used to fall over but that is well in control and faces the batter more,” he said. “At the same time, I did not lose my spin and drift, and my pace increased – all of which helped me.”

These, and an increased focus on his lengths, which he has credited for his success not only during the Asia Cup but also on India’s tour of the West Indies.

The increase in pace without a loss in turn means batters now don’t have as much time to read him off the pitch as the ball comes on quicker. Add to it his variations, and it leads to indecision.

During his devastating spell against Pakistan, Kuldeep tossed a ball up to Fakhar Zaman that rose above the batter’s eyeline, drawing him forward. But the ball dipped sharply and landed on a perfect length and zipped away, leaving Fakhar leaden-footed and getting an outside edge with a poke. Rohit Sharma spilled it at slip, but the delivery showed the threat that has made Kuldeep so hard to play again.

At 83kph, it wasn’t a particularly quick delivery for a modern spinner, but unlike before, the ball did not lose pace after pitching and skidded through, not giving the batter enough time to adjust.

He displayed this ability time and again in the West Indies, where he also used the wrong’un to great effect.

Anil Kumble: Kuldeep has ‘more body behind every ball’ now

The key, though, is the run-up, as Anil Kumble, legspin great and Kuldeep’s first international coach, explained.

“Even when I was the coach, Kuldeep had just come into the Indian team and we were trying to get him to bowl straighter. And hats off to him, he has been able to understand that that had to be done and he’s done that to good effect,” Kumble told ESPNcricinfo. “He is now running in straighter, which means that the body is more behind the ball that he bowls and that has certainly helped the pace at which he bowls now. Naturally, he doesn’t have to bowl quicker. It’s not that the arm-speed has suddenly become quicker.

“What is really good and impressive is that he’s always been a big turner of the ball so he is still able to give it a good rip. And because of the change of the angle of the run-up, it’s given him the advantage of body behind every ball.”

Kumble further said that the front arm coming down in line with his body instead of going across it has, indeed, given Kuldeep greater control.

Kuldeep will head into the World Cup after a special performance in the Asia Cup, where his nine wickets helped him get the Player-of-the-Series award, even though he got to bowl just the one over in the final after Mohammed Siraj blew Sri Lanka away with his opening spell.

Kuldeep was rested for the first two ODIs against Australia, with Rohit explaining the importance of “preserving” the lone wristspinner in his World Cup squad.

“Kuldeep is a rhythm bowler, we all know that,” Rohit said ahead of the Australia series. “But we thought of a lot of things and took this call. We have been looking at Kuldeep for the last one, one-and-a-half years, this is why we don’t want to expose him a lot.

“He is coming back for the last match. There are a lot of reasons. This is the best decision for us, to have him sit out for two games and play the third. We also have two practice matches [before the World Cup opener], so for the bowling rhythm, he will be back in it.”

With 31 wickets since the start of 2023, Kuldeep is the joint-highest wicket-taker in ODIs this year for players in teams that will be playing the World Cup in India.

Kuldeep is anyway a point of difference in a world-class bowling attack – Tabraiz Shamsi and Noor Ahmad are the only other left-arm wristspinners at the World Cup. And with his all-round improvement, he could well become India’s ace in the hole as they look to win a second home World Cup.