Tag: T20I

How many innings before we can accurately predict T20I Strike Rate?

Last time I looked at how long it takes for averages to mean something. Thought I’d try the same analysis for 20-20 Strike Rates. How long before a player’s 20-20 SR is a fair representation of that player?

Play for long enough and a batsman’s Strike Rate reflects their ability. However, in the early stages their career Strike Rate will be volatile as the sample is small. One significant factor is the impact of average on Strike Rate: most innings accelerate as they go on, so one big score early on will give a player a temporarily favourable career SR.

The below chart shows T20I Strike Rates for all players with 60+ Innings since 2009, split by their first ten, twenty or thirty innings (x axis) and then subsequent innings (y axis). Note that the acceleration in T20 scoring in recent years means most players scored faster in their later innings.

Consider the players who had a SR of 130 in their first 30 innings: one (Dilshan) stuttered and struck at 114 afterwards. Another (Nabi) scored at 156 per hundred balls in subsequent T20Is. If you have a player that has scored at eight an over in their first 30 innings, you may only know that they’ll score at between seven and nine per over from then on. Not very insightful.

Tom Banton has a T20 SR of 160 after 25 dismissals. That’s too few innings to be confident in him maintaining that scoring rate, but enough to say he’s probably a 140+ SR batsman.

Another recent example comes from Dawid Malan:

I don’t know what else I can do to break into the team for the T20 World Cup. I don’t know how you can be under pressure with an average over 57 and a strike rate over 150

Dawid Malan, Sky Sports Cricket Blog

Malan has done very well in his nine T20Is. Yet that tells us little about how we would expect him to perform in the future. Fortunately, T20 players get a lot of stamps in their passports- Malan scored at 145 per 100 balls in the Banglasdesh Premier League and 148 in the most recent Blast. It’s just a case of doing the legwork to calculate an expected Strike Rate at international level. I’ll leave it to the T20 experts to work out whether Malan is worth a spot in the World Cup squad.

Of England’s current players, only Roy and Morgan have more than 30 completed innings in T20Is. There’s insufficient international data. Yet most batsmen have played over 100 innings in T20 leagues – plenty to have a good read on them.

Summing up, there’s too few T20Is to use them to set expected average/strike rate in later T20Is. Far better to set this expectation based on club stats, adjusted for difficulty. There’s even enough data to weight analysis towards more recent performances. Also, beware small sample sizes: even 30 completed innings are too few. Anything under 100 innings and you should apply some judgement to the data.

Chart & Chat: A review of the 2010s

The 2010s end today. I’ve no team of the decade for you, just a chart and its implications.

Fig 1 – Batting and Bowling performances in Tests and T20Is this decade. Ratings are based on averages in Tests and Strike/Economy Rates in T20Is. Higher numbers are good – eg. India averaged 5% less with the ball in Tests than the average team. Ireland excluded as played too few games.
  1. The Big Three does not include England in Test Cricket. It’s South Africa / Australia / India based on the last ten years (and the last week).
  2. West Indies were not good at Test Cricket in the 2010s. Their record against the top three teams was W0 L21 D9. Problematic for the sport, if number eight can’t win in 30 attempts against the top three.
  3. T20Is will be closer than the average Test – As well as the obvious (one short innings rather than two long ones) the teams are far more evenly matched in 20-20 than Tests. Australia were one of the strongest teams this decade. Their W/L ratio was 1.5 in Tests but only 1.35 in T20Is.
  4. Bowling is not the differentiating factor in T20Is. This is odd, because weaker bowling should be punished by the six hitting machines out there in 20-20. Look at the distribution of the two colours of dots: the Orange ones for Tests form a line from the bottom left to top right. If you are strong in one discipline you will be strong in the other. It doesn’t work that way for 20-20: batting makes the difference.
  5. Two clusters of T20I performance: the top tier is Australia, India, England, New Zealand, South Africa. The next level down is West Indies, Sri Lanka, Afghanistan, Pakistan.
  6. What happened to New Zealand’s Test bowling this decade? Were they weak for a few years and I didn’t notice?

Please note that apart from points three and four, this chart is backwards looking: it does not have predictive power. Still, sometimes nice to take stock and see the wood not the trees. There’s a lot of noise out there, don’t miss the longer term trends.

Happy new year.