Training the Hawk-Eye on Axar Patel: Angular, Anomalous

Using never-before-seen ball-tracking data to study what makes Axar click.

When Ravindra Jadeja was ruled out of India’s home Test series against England this year, India chose a a like-for-like replacement in Axar Patel – handy with the bat down the order and accurate slow-left arm with the ball. At that point, he had played just 15 first-class games in the preceding three seasons of the Ranji Trophy, and seemed more suited to white-ball bowling, with his precise darting of the ball into the right-hand batter. Fast forward to the end of the year. Axar now has 36 Test wickets from 5 matches at a Lohmann-esque average of 11.86. He does not boast of the usual virtues of a long-format spinner. No appreciable flight, no big turn, no gorgeous loop. What, then, has made him so successful? The cricket commentariat has pondered upon this, and the conclusions are a bunch of reasons: lack of turn, undercut, and accuracy. Here, we will dive into ball tracking data to try and understand Axar’s modus operandi.

Using ball-tracking data enables us to follow the full trajectory of a delivery, including turn, drift, dip, speed and the various angles at which the ball is released and then bounces off the pitch. Such data is available for four of Axar’s five Tests, and we will try to use it to confirm certain ideas about his bowling and uncover new ones. All ball tracking data mentioned in this piece is updated till the 1st  India vs New Zealand Test at Kanpur.

Release

We start at the beginning: the release of the ball. Axar’s point of release is unusual compared to other left arm spinners, both in terms of height and the distance from the stumps. The first plot below shows the probability distribution of the height at which the ball is released, comparing the data for Axar (blue) with all data for slow left arm bowlers around the wicket (black). The two curves seen together show the relative odds of the ball being released from a given height by Axar and the average slow left-armer. Most of Axar’s deliveries are released from between 2.15 to 2.30 metres above the ground, which is very high compared to the usual release height for other slow left arm bowlers; bowlers of his kind seldom release the ball from that high. Such an oddly tall release compels the batter to track the ball from a height he normally doesn’t. Batting is based on familiarity, and Axar’s anomalous height makes his bowling slightly tougher to follow.

More than the height of release, it is the width of release that poses a greater risk to a batter facing Axar. His height and long arm-span together mean that he bowls from a height and from an abnormally wide angle. The plot below shows the probability distribution of the width of release – the sideways distance from the plane of the middle stump at the point when the ball is released. Here too, Axar stands a league apart from other slow left-armers. Most of his balls are delivered from 1 to 1.4 metres from the middle stump, whereas most slow left-armers around the wicket bowl theirs from 0.5 to 1 metres away from the middle stump.

This sharp inward angle creates doubt in the mind of the batter, who is always looking to play to protect his stumps. In addition, the angle also has implications for judging how to play for the ball turning away, as we shall see next.

Turn (Or The Lack Of It)

The most frequently talked about aspect of Axar’s bowling is turn, or rather, the lack of it. Ball tracking data shows that Axar’s deliveries indeed turn less than the average left-arm finger spinner in India. But this is not for the lack of putting revolutions on the ball. Spinners try to impart sidespin on their deliveries, which generates both drift in the air and turn off the pitch. Drift can be measured by the force on the ball in the air, which is directly related to the number of revolutions on the ball and how square the seam is rotating in the air.

The plot below shows the median turn obtained for a given range of drift force in the air before the ball pitches.  For instance, the leftmost point on the curves shows the median turn off the pitch for all balls that have a certain amount of drift force on them (in this case, 0.2 to 0.4 m/s2). To be clear, this is not the amount the ball drifts in the air before bouncing, but a measure of the actual drift force on the ball that results in its sideways motion in the air. For us, this is a proxy for the amount of sidespin on the ball.   

The black curve on the plot below shows that the amount of turn increases with the drift force on average, confirming that sidespin is crucial to both phenomena. Looking at Axar’s average turn, shown by the blue curve, for the same amount of drift, Axar gets a lower amount of turn than the average slow left-armer in India. Axar gets noticeably less purchase off the surface, regardless of the revs he puts on the ball.

The reasons for this are varied. As Karthik Krishnaswamy explains in this piece, Axar utilises “undercut” on the ball, which refers to releasing the ball with the palm facing upward, almost throwing the ball like a frisbee. Axar does this by rotating the ball into his hand before releasing it, which makes the spinning ball come out of his hand with the leather of the ball facing the pitch. As a result, sometimes the ball lands on the leather, gripping less, and turning less. Even when Axar releases the ball normally, with sidespin, the seam sometimes wobbles in the air, making the ball randomly land on the leather, which also makes it turn less.

This lack of turn contributes to Axar’s lethality. Among slow left-arm bowlers who have taken ten or more wickets in India, Axar has the lowest median turn on wicket deliveries, as the table below shows. It’s not that his wicket taking balls are arm balls. He does turn the ball away from the right-hander but gets very little turn on average.

The lack of big turn alone isn’t responsible for why Axar has been such a menace to right handers. Remember the extremely wide release points creating the sharp inward angles from around the wicket? Because of these inward angles, Axar’s deliveries continue moving into the right-hand batter after pitching, even if they turn out. The plot below shows Axar’s deliveries that have ball tracking data. On the x-axis, we have the turn off the pitch, in degrees. Almost all the balls have positive values for turn, which means they are turning away from the RHB. On the y-axis, we have the deviation of the ball from the point of pitching to the plane of the stumps, as calculated by the same ball-tracking prediction that is used for LBW reviews. Most of Axar’s deliveries have positive values on the y-axis, which implies that they continue moving into the RHB after pitching.

Batters play spin by trying to read the direction of turn from the hand and in the air. A batter facing Axar reads an outgoing ball from the motion of his fingers at release and confirms this by seeing the seam rotate towards the offside. The batter’s training kicks in, setting him up to play outside the pitching line of the ball because he expects the ball to move away after pitching. Here is where the deviousness of the sharp angle defeats him: the ball still goes in from the line of pitching, past the defense and into the pad or stumps. A great example is Zak Crawley’s LBW in the 1st innings of the third Test in Ahmedabad. The ball is delivered like an away-spinner, but it starts wobbling mid-air, reducing the purchase off the surface. This one actually turns – 1.75 degrees away, but the delivery angle means that it is still going 0.05 degrees into Crawley after bouncing.

Ball tracking data allows us to reconstruct the path of the delivery, making a visual representation of this ball possible. The figure below shows a bird’s eye view of the ball. The first panel on the left shows the actual track of the ball from release to bouncing as observed from above the pitch. Notice how wide the release is. The second panel then shows the angle of the ball when it was released as a blue line. The third panel shows the angle of the ball just before it pitches, as a grey line. Notice that the release angle and the angle before pitching are different – the ball has drifted in the air into Crawley, making the inward angle even sharper. Finally, the fourth and rightmost panel shows the path of the ball after pitching in red. Notice how the ball has actually turned outward. The red line makes an angle with the grey line, which was the path of the ball before bouncing: this is the actual turn obtained off the pitch. Although the ball has turned away, it continues moving into Crawley after pitching, beating his inside edge.

This illustration of the three different angles that a batter must play against while facing a competent spinner sums up the threat posed by Axar. Very few of Axar’s wicket taking balls are actual arm balls, but it is the extreme release angle coupled with the inward drift and slight turn, sometimes by design, sometimes via wobbly imperfect release, that beats the batter who conventionally expects the ball to move away or straighten on pitching. The table below shows the median deviation of a wicket-taking ball between the pitching point and the stumps for all slow left-arm bowlers who have taken 10 or more wickets in India (till the 1st India vs New Zealand Test at Nagpur). A positive value means the ball moves in, a negative one means it moves away. Axar’s values are extreme: his wicket balls move 18 centimeters inward on average.

Darting The Ball, Literally

While the anomalous release and the lack of outward movement is often talked about while discussing Axar, his trajectory is given less attention. Given the tall release, one would assume that batters are more likely to be on the front foot playing him, but ball tracking data reveals otherwise. Spinners usually flight the ball, throwing it slightly upward to get the loop they need. In contrast, Axar almost never flights his deliveries. Shown below are the distributions of the vertical speed at release, for Axar and all slow left-arm bowlers whose deliveries are available in the ball tracking data. A positive value means that the ball is thrown upwards, and a negative value implies it is thrown downwards. Almost all Axar’s balls have a negative value: he literally darts all his deliveries in.

Batters subconsciously use the trajectory of the ball to decide if they want to go forward or back. Axar’s flat dart-like trajectory compels batters to play back more often than they would facing other spinners. According to Hitting Against The Spin, a new book on cricket data by Nathan Leamon and Ben Jones, 83% of balls delivered by spinners in the 4 to 5 metre length are played on the front foot. The corresponding figure for facing Axar is 76%¹. About 70% of balls in the 5 to 5.5 metre length are played on the front foot, while facing Axar, only 51% balls are played on the front foot.

Lift: The Opposite of Dip

To create wicket-taking threats, this aversion to front-foot play combines with another anomaly of Axar’s bowling: the lift he gets. In addition to the sidespin that we covered earlier, spinners also put some amount of overspin on the ball by spinning it in the forward direction. As a result of this overspin, the ball experiences a downward thrust before pitching. This makes it land shorter than the batter initially predicts. Spinners can also get “lift”, which is an extra upward force on the ball, the opposite of dip. This can happen when the delivery is angled sharply across the pitch. Lift puts an extra upwards thrust on the ball, making it hang for slightly longer in the air, and therefore makes the ball pitch fuller than initially anticipated.

The plot below shows the distribution of dip or lift forces on the ball. A positive value of vertical acceleration means lift, a negative one means dip. As we can see, Axar gets lift much more often compared to the average spinner. This, again, is a direct result of the sharp angle of his delivery – the sharper the angle into the batter, the more the upward lift force on the ball.

This lift along with flat trajectory ensures a two-step trap for the batter. The flatness makes him move back, the lift makes the ball pitch fuller than predicted. The batter is now playing a full ball on the back foot – a recipe for disaster, especially because Axar bowls so quick – his median speed is 90 km/h while the median speed for the average slow-left armer is 84 km/h.

There are many examples of this mechanism bringing Axar wickets, like Dom Sibley’s leg before in the second Test in Chennai. That ball had a lift of 1 m/s2. This means that the ball had an extra upward force on it, which was 10% as strong as the pull of gravity downwards. As a result, the ball pitched a little fuller than it would have without the effect of lift. Sibley was stuck on the backfoot and unable to bring his bat down in time to a ball that ultimately ended up being fuller than he had initially calculated. Similarly, Jofra Archer in the 3rd Test in Ahmedabad tried to play an incoming ball on the backfoot. The lift on that was a humongous 2.2 m/s2, making it pitch much fuller than Archer had gauged from the flat trajectory. The speed meant that Archer, stuck on the backfoot, could not prevent it from hitting the stumps.

This lift also has a subtle role to play in the common front foot LBWs that Axar gets. Lift makes the ball stay longer in the air, which means it carries on along that sharp inward angle, giving it a better chance of beating the inside edge of the RHB. The dismissal of Ben Foakes in the 3rd Test in Ahmedabad involved a lift of 1.2 m/s2 on the ball, making it pitch fuller and crash into the pad going into the batter.

The Basics: Accuracy of Length

Finally, it is often said that Axar’s extreme accuracy contributes to his success. Screenshots of his pitch maps with tight bunches of deliveries abound on the internet. Ball tracking data allows us to quantify this and put an exact number on Axar’s precision. Since length is the primary determiner of a spinner’s success, I will look at the standard deviation of the length for different bowlers, which measures how much variance there is in the lengths they bowl. The lower this number, the more accurate the bowler is. Out of all the bowlers who have tracking data for at least 1000 balls and have taken 20 or more wickets, Axar is the most accurate, as the table below shows. His standard deviation in length is 0.85 metres.

Summary

In summary, freakish angles are central to Axar’s success. His extreme width of release and a lack of turn through natural variation make the ball come in even when it spins, beating the conventional way of playing spin outside the line if you think it will turn away. A flat dart-like trajectory hoodwinks batters into going on to the back foot. The exceptional lift he gets on the ball because of his sharp angles changes the length of his deliveries. To go with this, his extreme accuracy in length ensures full control and all this happens at high speeds, giving batters very little time to adjust. Although far from a conventional spinner, Axar succeeds through simple anomalies in a game based on familiarity.

1. Thanks to Shiva Jayaraman and S Rajesh at ESPNcricinfo for this data.