April 16, 2014

A measure for batting and bowling effectiveness in T20

Strike rates and economy rates do not quite tell the whole story. Introducing a new, two-dimensional method of assessing players in T20

Franchise-owner's dream: Chris Gayle and Virat Kohli have high Power and Certainty scores © AFP

The data used in this post is from all the games in the six seasons of the IPL. A player v player chart is available for each IPL game, and so is the number of dot balls, singles, twos, threes, fours, sixes and dismissals for each batsman and each bowler, and for each batsman-bowler pair is available. My thanks to S Rajesh for help with this data set.

Traditionally, batting in cricket occurs in innings, while bowling occurs in spells. Innings and spells have their own rhythms, their own specific phases. The disfiguring compression brought about by the 20-over contest renders spells and innings moot. Every ball counts. Dot balls are considered vital. The batting average, which tells us the number of runs a batsman makes per dismissal, is not necessarily important in T20; neither is the bowling average. Batting strike rates are deceptive, given the small number of deliveries in most single innings.

For example, a batsman could hit three sixes in an innings and still score 21 off 20 balls. Another batsman could score 21 off 20 with a single boundary. The overall effect of either on a team's fortunes could be very different from the other. In the latter innings, the strike would keep being rotated, and runs would also be scored at the other end. In the former, the batsman would probably play a lot of scoreless deliveries and use up overs valuable.

As Sidharth Monga argued persuasively, a batsman trying to fight off a tough period hurts his team terribly in a short 20-over innings. Much better to take chances. If the runs come off the middle or off the edge, like they did for Suresh Raina in the World T20 semi-final against South Africa, it's all good. Players who take a few balls to get going are a liability compared to players who are willing to take chances from the word go.

So how might we measure performance in T20? Most basically, three things matter in T20:

1. The proportion of the total available deliveries that are scored off.
2. The nature of these runs.
3. The cost of these runs in terms of dismissals.

The ideal T20 batsman would hit every single ball for runs, preferably to the boundary, and never be dismissed. The ideal T20 bowler would not concede a single run.

I propose a measure along two dimensions - "Power" and "Certainty" - which can be commonly applied to batsmen and bowlers.

Power is the number of runs scored per dot ball. For a batsman, the higher the Power the better. For a bowler, the lower the Power the better. Certainty is the number of balls faced per dismissal. For a batsman, the higher the Certainty, the better. For a bowler, the lower the Certainty the better.

A batsman can achieve a high Power score by scoring off a large percentage of the deliveries he faces, or by maximising the share of boundaries among his scoring shots. Here is a chart showing how strike rates of some individual batsmen in T20 compare to their Power score.

Most readers will be familiar with the strike rate being measured per 100 balls. I have simply reduced this to number of runs per ball (along the horizontal axis). The number of runs per dot ball is given along the Y axis.

© Kartikeya Date

Chris Gayle is arguably the classic batsman of the T20 era. In the IPL, he has scored 2512 runs off 1568 balls for a career strike rate of 160. This is the best strike rate for any batsman with more than 300 career IPL runs. MS Dhoni has scored 2243 runs off 1589 balls in the league, a strike rate of 141. However, for every dot ball he faces, Dhoni scores 1 run more than Gayle. Gayle has a Power score of 4.32, while Dhoni has a Power score of 5.35. Virender Sehwag, an opening batsman like Gayle, has a career strike rate of 160 and a Power score of 5.21.

Strike rate tells us less about a player's ability to score quickly and consistently than the Power measure. Failures hurt a player's strike rate less than they do his Power score. This is because failures tend to include a higher share of dot balls and lower share of boundaries, while set batsmen tend to score off a higher percentage of deliveries than new batsmen.

For example, consider the following two sets of five innings. Each produced 206 runs in 136 balls. (I'm assuming that all deliveries were legal, and all innings were not-outs.)

© Kartikeya Date

ESPNcricinfo's player-v-player data provides dot balls (which include deliveries off which extras are conceded and deliveries on which wickets fell). For the purpose of this calculation, these two types of deliveries are excluded from the calculation of the number of dot balls. A dot ball is defined as a delivery on which zero runs are scored and the batsman is not dismissed. I have chosen to do this because I use Certainty as a separate metric to factor in dismissal rate.

The best T20 batsmen achieve high Power along with high Certainty. These are batsmen who score quickly from the word go while being dismissed as infrequently as possible. Typically, these tend to be players who are willing to take risks from the outset. Virender Sehwag and Suresh Raina come to mind as examples.

The Power and Certainty figures over six seasons of the league as a whole are 3.49 and 21.8. This means that 3.49 runs are scored per dot ball, and a batsman is dismissed by a bowler once every 21.8 balls.

© Kartikeya Date

The same measures can be used to depict the effectiveness of bowlers. The best bowlers have the lowest Power and Certainty scores.

© Kartikeya Date

T20 games are recorded in great detail. Eventually, it should be possible to measure Power and Certainty scores by over, by batting position, by bowling position or bowling style. I will conclude this post with lists of players who fall into each category over the six seasons of the league. It is apparent that openers have lower Power scores compared to middle-order players. Power and Certainty scores could also be developed by season. This two-dimensional measure will provide a systematic shape to a 20-over innings and perhaps allow observers to assess risk within a 20-over contest. Perhaps it will also allow administrators to tweak the rules, just like they have in ODI cricket in recent times. Eighty-six batsmen have scored at least 300 runs in their IPL careers. Divided into four categories, the players are grouped as follows:

JOURNEYMEN: Power and Certainty worse than the median:
Parthiv Patel, Naman Ojha, Paul Valthaty, DB Das, Adam Gilchrist, Sanath Jayasuriya, Mandeep Singh, Tirumalsetti Suman, Aaron Finch, Eoin Morgan, Mayank Agarwal, Ashok Menaria, Johan Botha, Sunny Sohal, Piyush Chawla.

BIG HITTERS: Power better than the median, Certainty worse than the median:
Virender Sehwag, Yusuf Pathan, Yuvraj Singh, Ravindra Jadeja, Keiron Pollard, Dwayne Bravo, Ross Taylor, Albie Morkel, Abhishek Nayar, Jesse Ryder, Wriddhiman Saha, James Hopes, Azhar Mahmood, DB Ravi Teja, Daniel Christian, Harbhajan Singh, Laxmi Ratan Shukla

ACCUMULATORS: Power worse than the median, Certainty better the median:
Jacques Kallis, Sourav Ganguly, Tillakaratne Dilshan, Manish Pandey, Herschelle Gibbs, Manvinder Bisla, Graeme Smith, Sachin Tendulkar, Rahul Dravid, Robin Uthappa, M Vijay, S Badrinath, Ajinkya Rahane, Brendon McCullum, Manoj Tiwary, Venugopal Rao, Mithun Manhas, Swapnil Asnodkar, Ravi Bopara, James Franklin, Luke Pomersbach.

STRONG BATSMEN: Power and Certainty better than the Median:
Suresh Raina, Rohit Sharma, Chris Gayle, Gautam Gambhir, Virat Kohli, MS Dhoni, Shaun Marsh, Shikhar Dhawan, Mahela Jayawardene, Shane Watson, Dinesh Karthik, Michael Hussey, Kumar Sangakkara, AB de Villiers, David Warner, Ambati Rayudu, Brad Hodge, David Hussey, Matthew Hayden, Irfan Pathan, JP Duminy, Andrew Symonds, Cameron White, Saurabh Tiwary, Dwayne Smith, Kevin Pietersen, Angelo Mathews, Steven Smith, David Miller, Owais Shah, Stuart Binny, Faf du Plessis, Mark Boucher

Eighty-two bowlers have delivered at least 300 deliveries in their IPL careers.

STRONG BOWLERS: Power and Certainty better than the median:
RP Singh, Lasith Malinga, Amit Mishra, Dale Steyn, Zaheer Khan, Munaf Patel, Ashish Nehra, Ashok Dinda, Anil Kumble, Morne Morkel, Ryan Harris, Sunil Narine, Dhawal Kulkarni, Parvinder Awana, Doug Bollinger, Shaun Tait, James Faulkner, Farveez Maharoof, Wayne Parnell, Mitchell Johnson, Shakib Al Hasan, Dimitri Mascarenhas, Mohit Sharma

ECONOMICAL BOWLERS: Power better than the median, Certainty worse than median:
Irfan Pathan, Praveen Kumar, Harbhajan Singh, R Ashwin, Muttiah Muralitharan, Ishant Sharma, Murali Kartik, Shane Watson, Yusuf Pathan, S Sreesanth, Rahul Sharma, Brett Lee, Daniel Vettori, Dirk Nannes, Shahbaz Nadeem, Bhuvneshwar Kumar, Johan Botha, Iqbal Abdulla, Ramesh Powar, Glenn McGrath, JP Duminy, Alfonso Thomas

WEAK BOWLERS: Power and Certainty worse than the median:
Jacques Kallis, Siddharth Trivedi, Rahul Bhatia, Umesh Yadav, Manpreet Gony, Ravindra Jadeja, Ajit Agarkar, Pradeep Sangwan, Suresh Raina, Angelo Mathews, Andrew Symonds, Chris Gayle, Daniel Christian, Thisara Perera, VRV Singh, James Hopes, Ryan McLaren, Rohit Sharma, Pankaj Singh.

WICKET TAKERS: Power worse than the median, Certainty better than the median:
Piyush Chawla, Pragyan Ojha, Vinay Kumar, Albie Morkel, Dwayne Bravo, L Balaji, Shane Warne, Keiron Pollard, Shadab Jakati, Yuvraj Singh, Harmeet Singh, Azhar Mahmood, Jaidev Unadkat, Anureet Singh, Kevon Cooper, Roelof van der Merwe, Yo Mahesh, Chris Morris

Note again that this is how these bowlers and batsmen place over their careers. For individual seasons, some of these players will probably be slotted into categories other than the one they currently occupy.

Kartikeya Date writes at A Cricketing View and tweets here