Playing risky cricket

Earlier this month I blogged about how the loss of wickets shifts the chances of victory and the number of runs scored in the remainder of the innings. In this post, I’m delving into how the speed of a team’s scoring effects their chances of losing wickets.

In an ideal world we would have ball-by-ball data which would include data on what sort of shots players attempt, and I would expect you would see a trend where batsmen attempting a lot of aggressive batting (whether or not those shots turn into runs) would be at a higher risk of losing their wicket. Unfortunately we don’t have that data, so we can only rely on the total number of runs scored, and the number of wickets lost, in each over.

I have to make a few assumptions here:

  1. Teams don’t dramatically change their batting behaviour from over to over, particularly if a wicket hasn’t been lost. So if a team is batting in a risky manner in one over and this results in the team losing a wicket, they would be more likely to have been batting in a similar way in the previous over.
  2. There is a correlation between batting in a more risky way, and scoring more runs. So while we don’t have enough data to actually categorise play according to risk, we can use the run rate immediately before the loss of the wicket as a proxy.

I have over-by-over data for just over 4000 men’s Twenty20 matches.

Firstly, let’s look at every over in the data set (excluding the first over of each innings), and the number of runs scored in the previous over, to identify how many of those overs resulted in the loss of a wicket.

wicketrisk1.png

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Losing early wickets and chances of victory

I have a general hypothesis which I will be exploring throughout a series of blog posts in this season, and it is this: batting teams start with two resources (balls and wickets), and they spend those resources as efficiently as possible to convert them into as many runs as possible. Thus Twenty20 cricket isn’t just about scoring runs as fast as possible. You want to preserve enough of your wickets to be able to play a riskier game at the tail-end of the innings “spending” those surplus wickets to give you the capacity to score at a faster rate.

In today’s post, I want to explore the role of losing early wickets in determining how many runs a team scores, and their chance of victory.

As a taste, this graph shows the likelihood of victory for teams based on how many wickets they have lost after five overs:

wicketschance11.png

Teams that have maintained all of their wickets have roughly two-thirds chance of winning. Teams that are down one wicket are still favoured to win, but the chance of victory drops gradually further. A team which has lost four wickets has less than 20% chance of winning. There have only ever been six innings where a team had lost six or seven wickets after five overs, and in all six cases that team went on to lose.

Continue reading “Losing early wickets and chances of victory”