So, now the match is finished, let's take another look at how we can use the Runs/Wickets State to measure a player's contribution.
When Mitchel Johnson came in, the runs/wickets state was 218/6. Teams at 218/6 had gone on to win .294 of their Test matches.
Johnson and McDonald took the score to 381/7. Teams at 381/7 went on to win .389 of their Test matches. Thus, Johnson and McDonald in this wicket managed to increase Australia's chances of victory by .095.
Siddle was out next ball, but at 381/8 we're looking at .382 wins, so Johnson's score stays the same but Siddle gets a -.007. (We'll punish the player whose wicket falls with any negative, and share the credit for any positive.)
Johnson and McGain put on 7 runs, so at 388/9 we're looking at .396 wins. Johnson's score goes up to .109, McGain gets credit for .014.
Johnson and Hilfenhaus take the score to 422. But defeat in this match transforms a score of 422 in the third innings of the match from a .500 win to a .333 win. That's a big -.063 for Hilfenhaus? Or is it a plus .104 for both?
Ah, you see, you can't just use a single innings' score. You have to remember that in the third innings of a match a team is chasing a pre-existing state.
Anyway, for the purpose of this post, let's call the scores as follows:
Johnson +.109
McDonald +.101
McGain +.014
Siddle -.007
Hilfenhaus -.063
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Ultimately, what you need to do (and what I have done for ODIs) is examine each DELIVERY in the match. Each delivery increaseds the chance of success of one team by a value x and decreases the chance of success of the other team by x (ignoring draws which are just a pain in the neck as far as this kind of thing are concerned!).
ReplyDeleteGo through a match and apportion pluses and minuses for each ball to each player. Then tot them all up at the end of the match and - voila. This has the advantage of taking into account the state of the match.
So - if the scores would have been level on first innings at Cape Town, then the McDonald / Johnson partnership would have had a huge potential impact on the chances of an Australian win. As it was, they were so far behind, it didn't really have that much effect at all. I suppose the South African fielding positions would have been different too had the scores been level on first innings.
Benedict (SKY Sports Cricket Statistician)