Heading into last night’s second qualifying final, Bhuvneshwar Kumar’s head had a firm grip on the Purple Cap. The Purple Cap is awarded to the highest wicket taker in each IPL series and, barring Watson or Chahal taking a hatful of wickets on Sunday, Bhuvi will be the proud wearer of the Purple Cap for IPL2016.
How important are wickets in T20 cricket? Is there an alternative single way to measure the effectiveness of a bowler taking into account not just the number of wickets taken but the value of each wicket, as well as other critical measures such as the bowler’s economy rate and the state of the match at which he makes his contribution?
In this piece Cricmetric takes a different view on how the bowlers stack up in the 2016 IPL and concludes that maybe it should be the Fizz, and not the Bhuvi, who wears the funny coloured cap.
Top Wicket Takers
The chart below shows the list of the 24 bowlers who, up to and including last Wednesday’s eliminator, had taken at least 10 wickets in IPL2016. As mentioned, Bhuvneshwar Kumar headed the list with 21 wickets followed by the RCB pair of Watson and Chahal with 20 wickets a piece. Mustafizur Rahman is ranked 6th with 16 wickets.
What is the value of a wicket?
Intuitively, wickets at the start of the innings should be more critical than wickets at the end. Not only do early wickets give the bowling team early momentum in the innings, but they also usually mean the dismissal of one or more of the opposition’s top batsmen. The top ten run scorers in IPL2016 normally bat no lower than number 3 in their respective line ups.
The chart below shows the average benefit in terms of runs saved for the bowling team per wicket taken by over. Contribution Scores are used as the basis of the analysis.
As can be seen, wickets taken in the first five overs are worth, on average, around 8 runs each to the bowling team. Thereafter the average value of wickets drops as the number of overs increase, to the point where a wicket in the 20th over is worth on average 1.9 runs to the bowling team. Again this is intuitive as in many situations, a wicket in the final over is little more than a glorified dot ball.
Bhuvneshwar Kumar – Wickets
The following chart shows the distribution of Bhuvi’s wickets by over, as indicated by the blue bars and referring to the LH axis. While 8 of Bhuvi’s wickets have come in the first 3 overs, another 8 wickets came in the 20th over. By multiplying the number of wickets taken in each over by the average value per wicket per over (as indicted by the red markers) we can arrive at a cumulative value for all of Bhuvi’s wickets (as indicted by the black dotted line and measured against the RH axis). On this basis, Bhuvi’s 21 wickets contributed a total of 99.3 runs for his team.
DS Kulkarni Wickets
The chart below is prepared on the same basis but for DS Kulkarni, who took 18 wickets in IPL2016. 13 of Kulkarni’s 18 wickets came inside the first 4 overs with only 3 wickets taken after the 17th over. Therefore Kulkarni’s 18 wickets contributed a total of 126.2 runs on average for his team.
The following chart ranks the top 24 wicket takers according to the total value of their wickets taken. Kulkarni heads the list with 126.2 runs despite the fact that his wicket tally of 18 was ranked just 4th. Bhuvi’s ranking slips to 3rd when measured on this basis, while the Fizz’s ranking slips to 11th.
Of course, wickets are just one measure of a bowler’s success. In T20 cricket, if wickets are king then a low economy rate is just as royal.
The chart below shows the list of the same top 24 wicket takers but this time ranked by the number of dot-balls bowled (blue columns, LH axis) in IPL2016. Bhuvneshwar Kumar again heads the list with 117 dot balls, followed by the Fizz with 112 and McClenaghan with 111. The chart also shows the rate at which each bowler bowls dot-balls, expressed in terms of dot balls bowled per over (red markers, RH axis). Which measure is more important? Like the total number of wickets, the total number of dot balls is important to show the sheer volume of these gems the bowler delivered. However total wickets and total dot balls can also be skewed by the number of balls bowled. Showing dot balls bowled per over allows for a fairer comparison between bowlers of their ability to subdue batsmen. Both Bhuvi and Rahman bowled an above average 1.9 dot balls per over. Kulkarni bowled dot balls at the highest rate of 2.3 per over.
Again there is no point being a master of the dot-ball if every non-dot ball bowled sails into the stands. Hence the royal economy rate.
However instead of looking at economy rate, the chart below ranks the same top 24 wicket takers this time according to the number of boundaries conceded in IPL2016. Adam Zampa conceded by far the fewest boundaries however he also bowled by far the fewest deliveries (103) for the 12 wickets he took to make it into the top wicket takers list. Interestingly, Bhuvi and McClenaghan, who were ranked 1st and 3rd in terms of dot balls bowled were ranked second last and last in terms of boundaries conceded with 57 and 64 respectively. On the other hand the Fizz, who was ranked 2nd in terms of dot balls also ranked well (8th) in terms of boundaries conceded. The chart also shows the rate at which the bowler conceded the boundaries, measured in terms of the number of boundaries conceded per over. Bhuvi conceded boundaries at the average rate of 0.9 an over. The Fizz on the other hand conceded just 0.6 boundaries per over.
Overall Bowler Performance
So how do we put all these different perspectives together to determine who has been the most valuable bowler in IPL2016? What to say of Bhuvi who, among the top 24 wicket takers, has taken the most wickets, bowled the most dot balls but conceded the second most number of boundaries?
One way is to use Contribution Score analysis. Contribution Scores allow us to calculate the runs above average each bowler contributed to the team taking into account all aspects of bowling such as wickets taken and economy rate but just as importantly the state of the match at the time the bowler contributed in terms of bowling first or defending a score, the over being bowled and the opposition’s score in terms of runs scored and wickets lost.
Taking this approach provides the following ranking for bowlers who bowled at least 100 deliveries in IPL2016.
The Fizz tops the list with his performances with the ball, contributing 125.7 runs above average to his team, followed by YS Chahal (97.7 runs) and Watson (74.6 runs). Despite being the number 1 wicket taker, Bhuvi is ranked 18th on this list contributing a total of just 5.6 runs above average for his team. S Aravind, despite not featuring in the top 24 wicket takers, is ranked 5th in the list.
The chart below takes the same approach but ranks the bowlers according to the contribution score per ball. This removes any bias against players who might have had the best results in terms of contribution score per ball, but who bowled fewer deliveries.
The first two places are still held by the Fizz and YS Chahal, however Adam Zampa moves into 3rd place while Watson drops down to 5th. S Aravind again features highly and is ranked 4th.
Looks like whichever way you look at it, Mustafizur Rahman has been the standout bowler of IPL2016. Unfortunately, he will have nothing on his head to show for it. This will be of little importance to him of course if he has a ring instead.