Opening: platform or spring-board?
On England’s last tour to India in 2008, Alastair Cook and Andrew Strauss recorded a century opening partnership in their first innings of the first test in Chennai then came down to earth with a blob in their first innings of the next match at Mohali. In the game at Chennai, England were bowled out for 316. In the next game, without the leg-up of any sort of opening partnership, England totaled 302.
Observing these anomalies in the relationship of an opening partnership to the innings total had led me to research how influential the performance of the opening pair really is. By convention, the batsmen opening the innings represent one of the most crucial combinations in the sport. They face the opposition’s attack at its freshest and have the opportunity to set the tone for the innings and match.
This post is the second in a short series on opening partnerships and batsmen, which began with a review of the recent decline – since 2011 – in first wicket partnership scores.
I have selected as my sample for this exercise all Test matches since January 2003. I have considered only each team’s first innings – that is, the first and second innings of the match. In most cases, first innings have run their course, allowing a comparison to be made of the situation with one wicket lost and at the innings close. Innings three and four are much more likely to be curtailed by declaration, time or achievement of victory, making the required comparison misleading. 826 opening partnerships and innings totals have been analysed.*
The first chart shows the distribution of first wicket partnerships. The score with the highest frequency is 0 (7% of total). 29% of partnerships were broken by 10; 45% by 20. At the other end of the scale, 12% reached three figures. The mean score was 43 and the median was lower at 25.
The second chart shows the average innings total for every first wicket partnership score recorded from 0 to 415. The horizontal axis is not linear as it misses out scores for which no opening partnership was made (the lowest was 92). The darker, lower columns depict the opening partnership value.
To gain a perspective on how overall innings totals vary with opening partnerships scores, I split the data into three based on opening partnerships of 0-50, 51-100 and 100-250. In this last case, because of the lower frequency of scores, the analysis was based on ranges of 10 (e.g. 100-109, 110-119, etc). Lines of best fit have been added to the charts to show the relationship between the two figures.
Partnership 0-50: the average innings total where the first wicket was lost at 0 is close to 300. While many opening partnership scores have lower average innings totals than this, there is a clear association of increasing opening partnership and higher innings totals. The formula for the line of best-fit shows that for every run that the opening partnership increases, the innings total increases by more than two runs.
Partnership 51-100: across this range of scores there is also a positive association, although it is slightly less pronounced, with each additional run scored by the opening pair associated with an increase to the innings total of 1.8 runs.
Once the opening partnerships exceed 100, the addition of ten runs is associated with an increase to the innings total of nine runs. The association between opening pair and total score is weaker at this level of partnership.
It seems clear that the Cook and Strauss examples cited at the head of this post were exceptions from the general trend observed in the data. In its early stages, the opening partnership appears to have the potential to be a springboard for the innings as each run scored is associated with an increase to the innings total of over two runs. The association weakens as the partnership reaches three figures, so that from 100 upwards the additional runs scored by the opening pair see a lower number of runs ultimately added to the innings total.
I have tried to be cautious with my language in describing these data. But the title to the post does assume that there is a causal relationship between opening partnership and innings total. The logic to that argument is well understood; crudely: by blunting the opening attack the first wicket pair establish an ascendancy over the fielding side which the rest of the team can capitalise upon. However, as statistics textbooks insist, we need to recognise that:
evidence of correlation does not imply causation.
How could this be?
The size of the opening partnership and of the innings total may both be influenced by third factors, rather than themselves be causally linked. There may be more runs scored later in the innings, not because the openers got the innings off to a good start, but because the whole innings benefited from factors such as: a weak or out-of-form bowling attack; poor standard of fielding; favourable weather and pitch conditions. In this interpretation, the opening partnership is merely a platform on which the rest of the innings will be built, consistent with its context of opposition and environment. Whether this is the case, or whether the opening partnership directly influences the fortunes of the batsmen that follow is difficult to unpick in a statistical review.
However, what numerical analysis might not reveal, cricketing commonsense can discern. The opening partnership is acting as a springboard when, for example:
- the opening pair, perhaps on the first morning of the game, battle through to lunchtime against challenging new ball bowling on a lively pitch. By protecting the rest of the line-up from a potent bowling attack, the openers will have increased their teammates’ run-making potential.
- one or both openers takes the attack to a quick bowler who has the potential to be a threat. By forcing a bowler out of the attack, the openers have managed to disrupt the fielding captain’s plans, undermined that bowler’s confidence, with the potential to reduce his and his colleagues’ effectiveness.
Perhaps these are exceptions, which have the impact that all opening partnerships aim for, but in most innings must settle for providing a platform.
Are there examples you can identify where a test match opening pair have acted as a springboard for their team’s innings?
* The sample includes 125 innings concluded by declaration. The average opening partnership and innings total were higher for this sub-sample.
I excluded a small number of innings from the analysis where I decided the circumstances would not shed light on the relationship of opening partnership to innings total: one of the openers retired injured and so the opening partnership involved more than two batsmen (3); the innings was closed with the opening partnership unbroken (1); the innings was closed by the end of the game (8).
Acknowledgement: thanks to Michael Wagener, stats sage, for reading a draft of this article.