Beyond the strike

In his first guest blog for OptaPro, John Robertson introduces a new metric to assess batting performance.

Existing assessments of runs scored and strike rates can all too easily disregard bowling opposition, time spent at the crease and the wider context of an innings.

For example, there are constant debates over Virat Kohli and AB De Villiers and who is the superior batsman in T20 cricket. De Villiers has the better strike rate but Kohli has the higher average. This led to me proposing the concept of an adjusted score metric to put a quantitative value of what a batsman really contributed to their team’s total.

The metric acknowledges strength of the bowling attack, time spent at the crease, whether fielding restrictions were in place and finally how the batsman performed relative to the innings situation.

Adjusted score metric

Combined Strike Rate

‘The strike rate of the time batted’ helps to provide equality between batsmen who bat at times when players score faster such as the Power Play and batsmen at the crease when players score slower such as the middle overs.

*’Strike rate of time batted’ is the overall strike rate of the period in which a player batted. For example, if a batsman batted for 10 overs and 60 runs were scored then the strike rate of the time batted would be 100.

Top 15 run scorers, Indian Premier League 2016

Total Adj Score: total amount of adjusted score runs over the season
Total Runs: conventional measure of runs scored throughout the season
+/-: total runs scored subtracted from Total Adjusted Score
Adj Ave: Average Adjusted Score per innings

The adjusted score can be applied to show the comparative value of certain types of players in T20 cricket and where some batsmen are best utilised during the innings. The metric should be able to give a clearer indication on which batsmen are more valuable in T20 cricket and provide a more accurate assessment of their contributions with the bat.

Total Adjusted Score: Kohli Vs Warner

Despite Kohli’s record runscoring season, the metric significantly decreases the value of his runs. This came in part due to Kohli playing at the Chinnaswamy stadium, Royal Challengers Bangalore’s home ground. The ground has one of the smallest boundaries in the IPL and as a result enjoys many high-scoring games, which devalued some of Kohli’s performances. Warner, however, played in Hyderabad, a ground where only one team scored over 180 (compared to 12 times at Chinnaswamy).

Kohli’s lower adjusted scores also came about due to the fast scoring of the Royal Challengers Bangalore who regularly posted totals over 180. Kohli was a comparatively slow scorer compared to his team but when comparing him to the match strike rates his adjusted score increases significantly. Despite Kohli’s adjusted score being lower than his actual runs scored, he was still the most valuable batsman by average adjusted score per innings in the 2016 IPL.

Slow-scoring openers

Test batsmen have shown they can adapt to T20 cricket through scoring at a slower pace, providing an anchor for their team. It had been commonplace in the IPL for most teams to employ this tactic, with successful teams such as Kolkata Knight Riders and Rajasthan Royals often opting for conservatism in their use of Gautam Ghambir and Rahul Dravid respectively.

However with both finalists in the 2016 World T20 opting for big hitting openers, this approach is perhaps becoming dated. Winners West Indies selected Johnson Charles and Chris Gayle as their preferred openers, with England opting for Alex Hales and Jason Roy. While clearly a small sample, it does suggest that it may be time to move to a more expansive game.

During the 2016 IPL that theory was further reinforced with the three highest ranked teams all having at least one aggressive, fast-scoring opener. The Sunrisers Hyderabad had Warner, Royal Challengers Bangalore had Virat Kohli and Chris Gayle and the Gujarat Lions had Brendon McCullum, Aaron Finch and Dwayne Smith.

The two bottom-placed franchises, Kings XI Punjab and the Rising Pune Supergiants, used slower scoring openers Murali Vijay and Ajinkha Rahane, both of whom had strike rates below the league average (124 and 126 respectively). While both had good tournaments it can be seen in their adjusted scores that their value to the team was lower than their runs scored.

Reaching this metric

Here I will briefly outline some of the considerations that went into constructing this metric.

A limitation arose when using the strike rate of the time the batsman spent batting, such as Bhuvneshwar Kumar’s 21 off eight balls against the Rising Pune Supergiants.

This showed that Kumar’s innings was worth only marginally more than the amount of runs he actually scored despite the team’s strike rate for the entire innings being just 98.33. It also showed that Kumar was only five runs more valuable to the Sunrisers Hyderabad in that game than Naman Ojha who made 18 off 21 balls.

The limitations of adjusting the score by the strike rate were also exposed when a batsman came in and was the only player to face, meaning his adjusted score would be equal to his own runs contributed.

However, the combination of the three parts of the formula helped to showcase the value of a lower scoring innings. For example, in the World T20 final Marlon Samuels scored 85 off 66 balls, taking the plaudits, however Carlos Brathwaite’s innings is well recognised by the adjusted metric, suggesting they may not have won the game if not for this innings.

The adjusted score metric has shown value in helping us further understand the contribution of a batsman beyond traditional measures within the context of T20 cricket. Whether this can extend out into other formats of the game currently remains to be seen, and this development would form the next phase of this initial analysis.