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How do run-rates change across a T20 innings?

In the 13 years since its inception, T20 cricket has arguably become the most popular format of cricket across the world. Love it or hate it though, it has undoubtedly had a huge impact on how batsmen play across all formats.

Over the past five months, I have been building a database of ball-by-ball data for T20 events around the world. It currently consists of information for just under 290,000 deliveries covering all T20 matches since the start of 2014 as well as a number of matches from international level and the IPL and CPL from before 2014.

Across all of the matches, the average score is 144.9 runs in the 20 overs, suggesting an average run-rate of 7.25 through the innings. However, as anyone that has watched T20 cricket will know, the run-rate is not constant throughout the innings, so I thought it would be interesting to look at how it changes as the innings progresses.

We can see that the first over of a T20 is generally the lowest scoring of all the overs as the opening batsmen get used to the surface and do not want to risk giving away an early wicket. Indeed, it is the only over in a T20 match that averages a run-rate of less than six runs per over. This reticence from batsmen to attack early on may explain why many teams look to get an over from one of their weaker bowlers out the way here.

Once the first two overs are out of the way, the run-rate for Overs 3-6 in the powerplay are pretty constant, ranging from 7.55 in Over 3 to 7.75 in Over 6. During this powerplay period, only two fielders are allowed outside the circle, which explains why batsmen are more aggressive and able to score more runs in this period.

There is a significant drop-off once the powerplay ends with the runs-per-over dropping from 7.75 in Over 6 to 6.40 in Over 7. Indeed, the run-rate does not return to the powerplay levels until it reaches 8.05 in the 15th over of the innings. We can also see the acceleration as teams attack at the end of the innings as the graph continues upwards.

The drop-off in the last two overs in the second innings can probably be explained by teams either being in a comfortable position to win and not needing to go mad or being well behind and no real incentive to really attack.

The next question is whether the pattern is similar across different tournaments or whether teams structure their innings different in different competitions. The graph below shows the same, but broken down by tournament instead of innings.

There are some interesting features to note here. Firstly, we can see that there is a significantly higher run-rate in the powerplay overs in the T20 Blast in England than in either the IPL or the CPL. The T20 Blast averages 47.0 runs at 7.84 runs-per-over during the six powerplay overs, compared to 42.0 in the IPL and 39.3 in the CPL. Whether this is a feature of weaker bowling in the T20 Blast or whether it is a strategy to attack early is unclear, but it is something worth considering.

We can also see that batsmen accelerate more toward the end in the IPL, particularly in the final five overs of the innings. Throughout most of the innings, we see the T20 Blast ahead of the IPL, but once we hit Overs 16-20, the IPL starts to move clear. Could the higher run-rate earlier in the innings in the T20 Blast result in fewer wickets and established batsmen left later on? That is something to look at in the future potentially.

The CPL is an interesting tournament. It lags way behind the IPL and T20 Blast in terms of run-rate throughout most of the innings before they start properly hitting in the final over or two. Indeed, the 10.87 in the final over in the CPL is far ahead of any other over in either of the other competitions, but it is still only just enough to lift the overall innings average just over the 7.0 runs-per-over mark. Does this mean that the grounds are tougher to score on in the Caribbean? Maybe, although they are apparently easy enough to score off at the end of the innings. Does it mean that West Indian teams need to work on rotating the strike more often in the middle overs? Possibly.

This is only a brief first look at how innings are structured in T20 matches. There are obviously plenty of other factors to build into this - how many wickets do teams have remaining at different stages or are the grounds tougher to score on in certain areas are two, but there are many more. However, it gives an overview of how the run-rate changes across an innings and it may give some ideas of periods in which teams can look to improve their strategies.

1 comment:

  1. Hi,
    Do you have any stats on the most productive balls of the over? I get the feeling that batters like to score early in the over but cannot find stats to support this.


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