What makes Bhuvneshwar a threat?
If you were to make an assessment about a fast bowler, from a distance, what are the attributes that are likely to catch your eye? The first few would be a fast run-up, high jump, strong action, pace and bounce.
Those are exactly the virtues you won't find in India's best strike bowler at the moment. He gives the impression of just ambling in; his feet barely leave the ground as he loads up in his action. And since most of the time batsmen are on the front foot, it all gives the impression of a lack of pace. The wicketkeeper rarely collects his deliveries with the fingers pointing up, so even the bounce he gets isn't appreciable.
Prima facie, Bhuvneshwar Kumar has no quality that's likely to catch a layman's fancy. But to know his real worth, you need to stand at the other end with a bat in your hand. That's when you realise how one of the most innocuous-looking bowlers is also one of the toughest to handle, especially if he has the new ball and the pitch has a little bit of assistance for seamers.
So what makes Bhuvneshwar a serious threat?
Bowling close to the stumps and a high-arm action
Bhuvneshwar's approach to the crease reminds me of the great Shaun Pollock. Just like the South African, he gets really close to the stumps. The closer the bowler gets to the stumps, the tougher it gets for the batsman, for there are less pronounced angles to play with. The line of the ball is always in line with the stumps, which means the batsman has no choice but to play at most deliveries.
And if the positioning on the crease is complemented with a high-arm action, like it is for Bhuvneshwar, the problems increase manifold: you, as a batsman, can't play inside or outside the line of the delivery as you would for someone bowling with a round-arm action or from wide of the crease.
For example, if Lasith Malinga was bowling from close to the stumps with a new ball, a right-hand batsman would play outside the line of the bal, assuming that the ball would swing away from him. Similarly, you would play inside the line while facing Makhaya Ntini to account for the acute angle he created by bowling from the edge of the box.
Strong wrist position
The best way to swing the ball in the air and to get lateral movement off the deck is to release the ball with the seam bolt upright. The more still the seam is in the air, the better the chances that it will not only deviate in the air but also hit the pitch on the seam and dart around. While it sounds quite simple in theory, it's extremely difficult to execute, for to keep the seam upright at the point of release, the wrist needs to be strong and also right behind the ball. That's what Bhuvneshwar has; his immense control over his wrist allows him to not only release the ball with the seam upright but also allows him to make subtle changes (like pointing it towards slips or fine leg) by tilting his wrist to move the ball both ways. If you're able to do that with control, you will trouble the best batsmen.
A full length
Bhuvneshwar has neither the pace of Umesh Yadav nor the bounce of Ishant Sharma. What he does have is an understanding of the importance of hitting the right length time and again. He realises that since his strength is movement, he needs to pitch it a lot fuller, for the longer the ball stays in the air, the better the chances of it moving. Also, it's a length that batsmen, especially openers, hate in the early part of an innings. Bhuvneshwar is not afraid of being hit through the line and that quality allows him to find edges often, for it isn't possible for batsmen to always keep middling the ball when it is swinging.
While the match between West Indies and India is likely to be remembered for Virat Kohli's scintillating century, not mentioning the spell of quality bowling by Bhuvneshwar would be a grave injustice, for Chris Gayle, Darren Bravo and Kieron Pollard - the batsmen he dismissed - had the ability of changing the complexion, and perhaps the result, of the game.