NB: All speeds are in miles per hour.
In T20 cricket bowlers changing their speed is one of their key weapons. Adjustments in pace can disrupt the rhythm of a batsman’s swing and force them out of control of their shot.
Beyond a bowler’s average speed and fastest and slowest balls, there are very few methods by which to quantify and analyse bowling speed.
The best illustration of how a bowler uses changes in speed is a simple line graph, such as the one shown below for Rajat Bhatia’s bowling for Rising Pune Supergiants against Mumbai Indians in Match 1 of the 2016 IPL.
From this graph we can see that Bhatia’s speeds hovered between 65 mph and 70 mph for his first 11 deliveries before he changed it up regularly for his last 13 deliveries, dropping to almost 50 mph and reaching towards 70 mph.
Basic analysis of Bhatia’s bowling is displayed in the table below.
|Bowler||Average Speed||Median Speed||Fastest Ball||Slowest Ball||Range|
The table tells us that Bhatia had a significant pace range of 17.92 mph, however, it does not tell us how often or by how much he varied his speed.
Closer analysis of Bhatia’s bowling enables further quantification of his bowling speed on more detailed metrics, displayed in the table below.
|Bowler||Slower Balls||Faster Balls||Median Speed Change|
For this analysis we are considering slower balls to be deliveries that are 7.50% slower than the bowler’s median speed and faster balls to be deliveries that are 5.00% faster than the bowler’s median speed. 7.50% is used for slower balls and 5.00% for faster balls because bowlers generally operate closer to their maximum speed than their minimum speed. We are using median speed as the benchmark figure because it is a better representation of the most common speed than the average which is skewed by outliers.
So, in Bhatia’s case, slower balls are deliveries that are 4.92 mph below 65.70 mph and faster balls are deliveries that are 3.28 mph above 65.70 mph. The slower and faster ball data tell us that Bhatia bowled nine balls 7.50% slower than his median pace and three 5.00% faster. This corresponds with the illustration in the line graph with Bhatia’s troughs outnumbering his peaks.
The median speed change figure displayed in the table above tells us how much a bowler varies his speed from delivery to delivery. This is an important figure because it quantifies the extent of variation from ball-to-ball rather than against a median or average figure.
The median speed change is calculated by finding the speed change from one delivery to the next, ignoring positives and negatives, and then finding the median figure of those differences. Median is preferable to average because average is skewed by significant changes in pace and is therefore less representative of typical speed change.
These two sets of data: slower and faster balls and median speed change enable a comprehensive assessment of bowling speed.
The number of slower balls and faster balls reveals how often a bowler makes significant changes of pace while the median speed change reveals how much a bowler changes his speed each ball.
When analysing median speed change it is more helpful to look the change as a percentage of the bowler’s median speed because that places the change in the context of that bowler’s regular speed. In Bhatia’s case therefore, his median speed change of 3.83 is divided by his median speed of 65.70 and multiplied by 100 to give a figure of 5.82. In the chart below this is displayed as Speed Change Rating.
SCR enables comparisons of speed change between bowlers regardless of their median pace and would allow us to ascertain which bowler changes his speed the most from ball-to-ball. This data could be analysed with regards to a single bowling spell, innings, tournament, or career.
Using the methods described above we have analysed four more bowling performances that have been hand-picked to illustrate different uses of bowling speed.
|Bowler||Slower Balls||Faster Balls||Speed Change Rating|
Ishant Sharma’s SCR of 3.17 indicates he changed his speed slightly ball-on-ball. The graph below shows a number of balls delivered below his median pace but only two were slow enough to register as slower balls.
Harbhajan Singh has the highest SCR of the five bowlers, indicating he changed his pace regularly and significantly and this is supported by the line graph. He favoured bowling quicker balls to slower balls.
Mustafizur Rahman is famed for changing his pace regularly and that is supported by the data which gives him the second highest SCR of the five bowlers. Interestingly the data has him bowling more faster balls than slower balls – this is perhaps because he is a seam bowler who regularly operates below his maximum speed.
Adam Milne’s SCR of 1.80 indicates he very rarely changed his pace, and the graph below supports that. The graph, with five troughs, does suggest that Milne bowled five slower balls, not three, but those two balls, recorded as 82.63 and 82.86 mph were not 7.50% slower than his median speed of 88.45 mph.
It is important to note that SCR, displayed without slower and faster ball data, could be misleading. For example, if a bowler’s first 11 balls were all of varying speeds but the remaining 13 deliveries all a very similar pace, that bowler would have a low SCR because their median change would be very low, despite almost half their deliveries representing significant changes in pace. This is because SCR is designed to show a bowler’s most common speed change ball-to-ball, not an average speed change. When SCR is displayed alongside slower and faster balls a comprehensive analysis of a bowler’s speed is given.
Freddie Wilde is an analyst at CricViz.