Developing a bowling value index
While looking back statistically over the career of the recently-retired Brett Lee, I mused over ways of assessing the value of bowlers to their team. Lee, of course, was a fast bowler best used in short spells, and was not one who one would use to plug up an end and bowl all day. He thus had quite a good strike rate (10th in the list of 35 Test bowlers with 250 wickets or more), but for limited times of the playing day only. He only bowled 21.25% of the balls bowled while his team was fielding, ranking him only 25th in the same list of 35 bowlers. Obviously, his value to his team would have been enhanced if could have bowled more while preserving his strike rate - but there is a risk, of course, that the strike rate diminishes if a bowler is asked to bowl more.
I am thus inching towards a statistical measure of the value of a bowler, V, that is a function of Strike Rate (balls per wicket), i.e., V = k(SR)
where k is a constant representing the amount of bowling a bowler does.
The simplest way to calculate this is to divide the proportion of overs that each bowler bowls for his team by the strike rate. Thus for Lee, V = 21.25/53.33 = 0.398
The table below displays the value of V for each of the 35 bowlers with 250 Test wickets or more:
* % tbb represents percentage of teams balls bowled by the bowler
|Bishen Singh Bedi||266||80.32||27.75||0.345|
Murali was clearly, under this measure, the most valuable bowling commodity to his team in Tests - not only does he possess a strike rate more in tune with that of strike fast bowlers (compare it with Kumble, Bedi and Vettori, for example), but he bowled an extraordinarily high percentage of Sri Lanka's overs in Tests in which he took part, bowling one over in three.
It would appear, too, that Dale Steyn is forging a career that will put his name up in lights alongside the great bowlers of yesteryear. No one can question Hadlee's high index, given his value to an otherwise unexceptional New Zealand team, while the high positions held by Warne and McGrath formed the basis of Australia's period of domination in the first decade of this century. Similarly, Waqar and Wasim formed a potent Pakistani partnership as did Marshall and Garner for West Indies. The recently-retired Lee is where you might expect him, about half-way down this list, just outside the indices of the really great bowlers. The index of Kallis is significantly below those of others in this table, just emphasising that there are limits to what even great all-rounders like the South African can do. An index of around 0.4 seems to separate the really great bowlers from those who were perceptibly less so.
The following table gives the same results for those Test bowlers with between 100 and 249 Test wickets (min V = 0.4):
Lohmann and Turner bowled in conditions that are rarely replicated today, small innings totals allowing them to bowl a greater proportion of overs, and with a more potent strike rate. Barnes is confirmed as the genius he truly was, while the index for Saeed Ajmal is interesting, and may in time, if continued, allow him to be classified as an all-time great.
The bottom five in this list are also of interest:
At the risk of destroying the reputation of an icon, the placing of Sobers at this end of the table really does suggest that history may be overrating his contribution as a bowler. The jury is still out on whether he or Kallis has been Test cricket's greatest allrounder - but that is a topic for another day.
The complete list of the statistical measure V for all bowlers can be downloaded here