Wednesday, August 13, 2008

Bowlers as they get more experienced

There was a comment from Gary Naylor here saying that Monty Panesar should improve on his average of 32 as his career goes on, since he'll learn more about how to bowl.

I'm not convinced. I took all spinners with 149 or more wickets since WWII, and found split their wickets into which Test it was in their careers, so I could find the overall average in debut Tests, second Tests, third Tests, etc.

To get rid of some noise I actually took a five-Test moving average, so the first data point in the graph below is the overall average in the spinners' first to fifth Tests, the next the average in their second to sixth Tests, etc.

Also I weighted wickets by the average of the batsmen dismissed.

The down-then-up shape is more dramatic if you do a ten-Test moving average.

Note that there's a bit of a selection effect going on. I'm only looking at spinners who were good enough to play enough Tests to take 149+ wickets. Towards the right-hand end of the graph this is also a factor — if you imagine it continuing further on out, you'd eventually just be plotting Warne, Murali, and Kumble. There are, for those interested, 24 bowlers going into Tests 1-36, then 23 in Test 37, 22 in Tests 38-43, 20 in Test 44, 19 in Tests 45 and 46, and 18 in Tests 47-49.

I don't know how much I want to read into the graph, though I'm happy in saying that spinners improve after their first ten Tests or so. After that there may or may not be a trend — batsmen working them out? Certainly there's no strong evidence that Panesar will improve significantly (he's played 33 Tests), though of course it's possible.

Here's the corresponding graph for pacemen:

R^2 of 0.38 with a linear fit

There are 46 bowlers going into all of those data points. There's a downward trend — pacemen tend to get better with experience, at least for a few dozen Tests.

One thing to try in future is age rather than Test experience. The people who've done this sort of analysis in baseball say that age is a better thing to use than Major League experience. But of course baseball is not cricket, so I'm not sure what will come out of it.

Interesting David. I'd also try years of playing experience (years since debut), because we are getting some subtle distortions of age/experience with the glut of cricket right now. Grimmett, for instance, just scraped 200 wickets so that represents both his upward improvement and end of career decline. Panesar, like Brett Lee, might only start maturing from 200 onwards.

Incidentally, tracking a running average as a percentage of career average is probably a wiser analysis here as well. The longer the graph goes on the better the bowlers it is tracking (in theory anyway), so it might start tracking down instead of up).
That's really interesting, and runs completely counter to the generally accepted wisdom about spinners getting more canny and effective as time goes on... so I'd love to see the same work done with age/playing experience.

I'm not sure about playing experience though now I come to think of it. Are we seeing more bowlers like Stuark Clark who are debuting later on in their first class careers ? or Sidebottom if he'd never had that solitary first Test?

To move away from statistics, Panesar really seems to need someone to take him under his wing and make him start thinking about the game more. He just doesn't seem to think well enough on the field given his natural talent. Bowlers like Kumble and Vettori illustrate just how important it is to be a smart bowler, not just a talented one...
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