MS Dhoni isn't the ODI batsman he once was. The reason is that two of the primary pillars for his success over the years have developed cracks, and at 37, it's not easy to find a quick fix.

Early in his career, Dhoni's hitting was characterised by clean strokes, with a heavy bottom hand and quick limb movements. The swing was smooth, the follow-through easy. There were a lot of punches and jabs, and massive strokes, especially to spinners, after he gauged the length early. Apart from the "helicopter", he hardly played the sort of shots - laps and scoops, for example - that come so easy to the typical modern batsman. He overcame the textbook with hand-eye coordination and bat speed, both outstanding.

In the middle phase of Dhoni's career, he showed off his skill at milking runs. Good placement and hard running often saw him creep up to 40 off 40 without much risk. The risk-free approach laid the template for his best innings: get in and take it deep. It made him one of the best ODI players of all time.

Dhoni today falters because the ability to steal singles and then hit the big shots at will to release the pressure have waned. The prods are often limp and find fielders, fast balls die off his pads, and his big hits look like they need more effort than before.

Here's a look at his run scoring by phase of innings:

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Dhoni was always a slow starter, as shown by his dot-ball percentage in the first 15-20 deliveries at the start of his innings. Before 2015, as his innings progressed, there was a steady drop in the number of dot balls he played, which is not the case now: he consistently plays more than 50% balls for dots at all times at the crease.

Earlier Dhoni would prance down to spinners in the middle overs, and use both sides of the pitch to weave out gaps. This would ensure a constant change of strike and a steady flow of runs even when the boundaries were not coming. This can be seen in the percentage of singles and twos, which peaks for the older Dhoni after the 15-ball settling-in period.

What ails Dhoni now? A look at his strike rates against different styles of bowling is revealing. It drops across the board, but sharply against spinners.

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Legspinners rule the roost now, which means fewer balls turn in to him. More importantly, the world is wiser now: spinners have found the optimal trajectory to keep him quiet. A quick dart on a good length and Dhoni ends up blocking, stuck in no man's land. He cannot reach the pitch of the ball to thwack it or place it off his pads, and he cannot free his arms. The result: strings of dots that build pressure, emboldening the bowler further.

Against pace, Dhoni was known for the straight hits to full balls - those magnificent swings of the World Cup-winning variety. They were on display when India beat Pakistan 4-1 in 2006, where Mohammad Asif and Co were put to the sword. Here too, the world has learnt how to counter him. Almost no balls are bowled in his arc these days. The wide yorkers and the good-length balls that cut into his body are enough to keep him quiet. With his hand-eye coordination weaker than it was, he cannot hit the faster bowlers cleanly, even when the ball is full.

His conservative game means he hits out less often, and when he does, he loses shape, trying to hit too hard. This isn't infrequent. Dhoni's game was built upon taking it deep, but his ability to hit himself out of that pressure hole defined him. Now, with the hitting less reliable, he digs himself into a hole all right, but fails to climb out as easily as before. Even his boundary-hitting is noticeably diminished.

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Of late, he has failed to develop a response to what the new age has thrown at him. Bowlers have evolved, Dhoni's methods haven't. And in an age where teams start hitting from the get-go, this could be an issue for India in the World Cup.

This is a reality one has to accept. The other reality is that Dhoni is going to play the 2019 World Cup.

So, in what sort of situation is he the most useful?

In the build-up to the World Cup, India have faced a variety of circumstances, and in the typical tricky chase, or in the case of an early batting collapse, Dhoni has proved to be more than valuable.

The sedate Dhoni has mastered survival in dire circumstances: coming in before the 21st over, he has made 53 runs per innings since June 2015, but at 4.50 runs per over. Four out of six such instances where he came in in the first innings have been in matches won by India. The two losses were collapses to Bangladesh and Sri Lanka.

As a consolidator, Dhoni works in the first innings, taking it slow, protecting his wicket, and guiding his team to a respectable total. In chases, he averages 40 runs per innings coming in before the 21st over, playing 62 balls on average. India have lost six out of 13 such games, and in all of them, Dhoni's run rate has been lower than the rate at the point when he arrived at the crease. These include momentum-murdering knocks such as the 54 off 114 against West Indies, the 51 off 96 against Australia, and the 39 from 65 balls against New Zealand. Of the seven games India have won, three of Dhoni's innings were long, quiet knocks on tricky pitches, with Hardik Pandya, Bhuvneshwar Kumar and Kedar Jadhav playing the faster innings.

In low chases, he again plays the anchor when coming in early, often guiding India to wins:

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Steep chases are when Dhoni becomes the biggest liability. Send him in too early and the time he takes to settle will inflate the asking rate. Send him in too late and he will not have enough power to finish the chase. India have lost 11 of 16 games chasing over 280 since June 2015, with Dhoni's run-rate difference falling to negative in almost all those innings. In wins, someone else has usually upped the scoring.

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In chases, his proven method of biding time before exploding has found scant success if there is no hitting from the other end. It seems like Dhoni cannot pull off those lone-wolf miracles to close a chase anymore.

So, if India's high-worth top order is broken, it makes sense to send Dhoni in as early as possible, optimally at four, so that he can shape the first innings, or guide the second. But it is equally important to have a buffer in the lower order - players who can play at a brisk rate as Dhoni holds an end up. In chases of over 300, Dhoni, left to his devices, is likely to be a liability, and not the power-hitter he is reputed to be.

What, then, of his role, as a first-innings finisher?

Let us restrict ourselves to matches when he comes in after the 34th over. In 15 first-innings knocks, he has made 20 runs off 17 balls on average. He has faced 32% of the available balls from the point of the innings when he walks in, on average. In 2019, that is simply not good enough while setting targets. In the seven chases when he has walked in late, he has averaged ten runs per innings, five of which have come at Nos. 6 or 7. This is seen in the fall of his strike rate against right-arm pace in the death overs (last ten) of a first innings:

MS Dhoni v different bowler types Style Before 2015 After 2015 Left-arm pace 162.18 174.13 Right-arm pace 155.67 136.60 Right-arm legbreak 75.60 170.00 Slow left arm 110.67 115.38 Right-arm offbreak 135.10 112.50

If a platform has been set by the top three or four, and India are, say, 240 after 35 overs and looking at 350-plus, Dhoni isn't the right man for the job, for the reasons mentioned earlier.

So the question of how to use him comes down to smart handling, and having a grip on probabilities.

The chances of a set platform, or a steep chase, are high on the kind of pitches England has served up recently. Dhoni needs to be smartly used, or even hidden, in such cases. On the other hand, if the ball moves around early, and India find themselves in trouble, Dhoni is the wall they need. If they are rocked in a tricky middling chase, Dhoni can be their perfect guide. With a marauding top order and flatter pitches, the chances of the latter are low, but can you take chances in a World Cup?

India have an optimisation problem on their hands: how frequently will grim situations come about? Is it worth keeping a power-hitter out of the XI because of that fear? Can India's lower order and bowlers combine to carry a passenger with the bat in most cases? How these questions are answered could be the key to India's progress at the World Cup.