The replay comes up in slo-mo for us to get a closer look: Brett Lee runs in and bowls a short-pitched delivery at 150kph. Sachin Tendulkar seems to have all the time in the world to get into the right position - he goes back and across and plays it right under his eyes. The pace at which the TV camera reruns it makes it look a cakewalk, an everyday shot, but the batsman gets only a fraction of a second to judge, decide and execute. What is it that enables the likes of Sachin to tweak their responses and plan their shots?

Let me break it down further for you. At the point of release a batsman must ascertain the line and the length of the delivery, must weigh his options with regards to his response (attacking or defensive) and then move quickly to get his body into the right position to execute the option chosen. One of the principles of batting is to be prompt and to be in a position to receive the ball, as against arriving at the same time as the ball, because that is invariably too late. The quicker the bowler, the less time you have in hand to act. If the batsman fails to get his calculations right in time, he is most likely doomed. Unlike against slower bowlers, with whom you may have a second chance.

Judging the length and line
If judging the length and line early makes batting relatively more easy and effective, failure to do so puts the batsman at a disadvantage.

To judge the length, the batsman must watch the point of release of the delivery. The earlier the release, the fuller the ball, which in effect means that if the bowler delivers the ball at the first point of release, it would result in a beamer. Every subsequent delay in release would mean a reduction in the length, with the bouncer being the last point of release. That's the reason every batsman is taught to be ready for the full ball first, because that's the first possibility; if the bowler passes that point of release without delivering, the mind starts sending the body signals to be prepared to go on the back foot.

Batsmen around the world are brought up playing bowlers with high-arm actions and hence their minds are attuned to trying to ascertain the length by looking at the point of release. But if you're up against someone like Lasith Malinga or Shaun Tait, both of whom have slinging, round-arm actions, it's simply not possible to know the length for sure at the time of the delivery, as there is always a doubt about whether the release was early or delayed. The angle at which the arm comes down leaves a lot to the imagination; unfortunately, though, there isn't much time to imagine at their pace.

Another important aspect that influences the ability to judge length is the position of the batsman's head in his stance. Ideally the head should be still and the eyes level to be able to judge the length correctly. If the head is tilted upwards, even slightly, all deliveries might seem short-pitched.

Next comes the line. Batsmen try to keep a close eye on the bowler's wrist at the point of delivery and the position of the wrist with regards to the crease. In the case of a fast bowler, the tilt of the wrist may help send the ball in the direction in the direction it is tilted towards. When Ishant Sharma's wrist tilts towards the on side, you're more or less sure the ball will swing in to the right hander. This isn't foolproof, though, especially when the ball is reverse-swinging. Waqar Younis used to keep the wrist completely upright, or even slightly tilted towards the off side, while making the ball dip in to the batsman.

Wrist position is a good giveaway when it comes to reading spinners, many of whom cock their wrists to bowl topspinners. Similarly, the back of a legspinner's hand will usually face the batsman when he tries to bowl a googly. These variations are subtle but if observed and decoded accurately, they can help the batsman.

Makhaya Ntini's wide-of-the-crease action gave away the angle of his stock deliveries, which came in to the right-hander, while Glenn McGrath's close-to-the-stumps action ensured the ball stayed on a well-defined line around the off stump. An offspinner will usually prefer to come in close to the stumps to bowl the topspinner or floater.

While the wrists and the action will give you clues, keeping a still head in the stance, almost in line with the toes, is vital to your ability to judge line correctly as a batsman. The moment the head starts falling over, the lines get blurred - a problem Rohit Sharma is facing at the moment. Since his head is falling over, he's either chasing balls that should be left alone (in the first ODI against New Zealand) or finding the ball finishing in line with the front pad instead of in line with the downswing of his bat. From there on it's just a matter of when and not if he misses one.

Swing and drift
Batsmen also try to look at the way the bowler has gripped the ball, with regards to the position of his fingers and the orientation of the shiny surface. When bowling a slower one McGrath would hold the ball with his index and middle fingers split wide apart; Lee while doing similar would hold the ball deep in his hand. Zaheer Khan often bowls with his fingers across the seam, which tells you to be ready for a straight delivery because the ball won't swing unless the seam is upright.

One of the principles of batting is to be prompt and to be in a position to receive the ball, as against arriving at the same time as the ball, because that is invariably too late

The shiny surface, if visible, often gives away the direction in which the ball will move in the air. For instance, an offspinner's drift can be read by looking at which way the shiny part of the ball faces. If the ball is swinging conventionally, it will drift into the right-hander if the shiny side is outside, and vice versa. Keeping the shine facing the palm not only takes the ball away in the air, it also makes it skid after pitching, as the ball lands on the shiny side. Obviously, looking at the shine doesn't help much if you're up against the likes of Muralitharan, or someone who prefers to bowl with a scrambled seam.

Leg position
Once the line is deciphered, a batsman will mostly try to keep the front leg outside the line of the ball. For a right-hander the front leg must stay leg side of the ball. If the leg is not in the appropriate position, the bat will never come down straight, and you might end up playing across in front of your pads. Also, keeping the leg outside the line is mandatory to maintain good balance, or else you risk falling over.

There is a good chance, though, that these lines will get blurred when the ball's swinging or spinning too much. Murali and Warne have wreaked havoc because batsmen were never sure of the amount of turn off the surface while facing them. What started out seeming the correct place to plant the front foot often proved incorrect in the end. It's the same when the ball is reverse-swinging. Haven't we seen Waqar and Wasim hit people on the toes umpteen times?

Things are slightly more manageable on the back foot, because not only does the short ball give a little more time to adjust, it also doesn't swing as much.

The role bounce plays
Tall bowlers with high-arm actions, like McGrath, Ambrose, Kumble and so on, tend to generate more bounce than their round-arm, slingy counterparts like Malinga or Ajit Agarkar. While tall bowlers get consistent high bounce, it also often misleads the batsman into playing on the back foot, even to balls that are meant to be played on the front foot; this results in them getting trapped in front. On the other hand, bowlers like Malinga and Agarkar pose a different kind of threat - you can never trust the bounce with them. Playing horizontal bat shots and ducking - for both of which you need to be able to trust the bounce - are difficult while facing these bowlers. You have to tell yourself to be on the front foot, even if the length and pace are pushing you back, and also to play with a vertical bat as much as possible, to make up for the lack of bounce.

Then there's the rare breed of freakish actions, which take a while to make sense of. Remember Paul Adams and how he took the world by storm initially? He was bowling normal chinamen and wrong'uns but batsmen were hopelessly caught in the flurry of limbs. Such actions are a batsman's nightmare when you're up against them for the first time. Your brain will eventually find ways to look for certain nuances to decode the mystery. That's why it's important for these bowlers to keep evolving, because once the novelty wears off, they become easy pickings.

Former India opener Aakash Chopra is the author of Beyond the Blues, an account of the 2007-08 Ranji Trophy season. His website is here and his Twitter feed here