Bowling Quality Index re-visited: incorporating home/away and recent form
This is the first of three very important and significant articles on batting performances against differing conditions and players.
About six months back I had come out with an article on Batting performances against different Bowling groups based on BQI (Bowling Quality Index). Notwithstanding the fact that it was a rough unpolished stone, it was one of the best received of all my articles and I came out with a follow-up article after doing some amount of polishing. However there were so many valid suggestions and great ideas that there is a need for me to re-visit that theme, this time incorporating improvements and new ideas. These tweaks would define this very important theme once and for all.
I have summarized below the ideas and suggestions. This is the extract from hundreds of comments.
1. The Bowling quality was determined based on Ctd (Career-To-Date) figures. That was very essential. However there is a clear need to do this work based on Ctd-Home and Ctd-Away figures depending on where the Test was played. As has been shown later, bowlers are poor travellers and these changes will make a significant difference.
2. The initial phase of the bowlers, during the period when the bowler is yet to take the first 50 wickets, has to be done correctly with no ambiguity. Most bowlers who had captured quite a few wickets in their Test career were nearly as good from day 1 and this fact has to be recognized.
3. Almost all bowlers go through widely varying form swings in their career. This important factor of Recent Form has to be recognized, based on their performance during their last 10 Tests, usually an year or so.
4. Bowling quality is not enough to determine the value of batting. The type of pitch plays a very important fact. Scoring a 200 at Lahore during 2006 is equivalent to a 100 while scoring a 100 at Hobart last week is the equivalent to scoring a 200. It is also essential that this should not be considered as a stand-alone measure. It is necessary to combine the two measures. Facing Marshall and Ambrose at Faisalabad on a batting wicket is quite different to facing Prabhakar and Prasad on the same pitch.
All this means that this coverage cannot be completed in one article. It would require three articles. In this one, the first, I will talk about the revised Bowling Quality Index based on Ctd-H/Ctd-A values and adjusted by Recent Form values. In the second one I will cover in depth how the Pitch Index will be calculated, using both Top-7 RpW (Runs-per-wicket) and BpW (Balls-per-wicket) values. Once the stage is set, the third article will revert to the Batting performances against a combination of these two measures. Thus there will be opportunity to come with your comments on the whole process. All three articles will follow in one unbroken sequence so as not to lose the threads of discussion.
Streamlining of Bowling Quality Index:
First, the handling of the first 50 wickets has been streamlined. Until a bowler, who has captured 87 or more wickets in his career, reaches 50 wickets, he is protected to the level of his career average. If he has done better than his career average, like Brett Lee, that is considered. This is very fair to established bowlers. Of course the other bowlers will have notional figures during their first 50 wicket-period. Why 87, why not 100 ? The number 87 has been considered to get world-class bowlers like Mailey, Spofforth, Richardson, Patterson, Hawke, Bond, de Villiers et al into this group. If this is termed as arbitrary it is no more arbitrary than setting the cut-off at 100 wickets. What is the sanctity about 100 wickets anyhow?
Most of the top batsmen travel well. In other words their home and away batting averages do not show very high degree of variation, as described below. I have selected 6 batsmen who represent the best in Test batting from different angles.
Average comparison for selected batsmen
|Batsman||Career Avge||Home Avge||Away Avge|
Even for Lara and Ponting their variation away from career average seems to be only around 10%. Bradman and Dravid have in fact performed better away to a significant extent.
Now let us look at a similar tables for bowlers. They seem to be poor travellers. I have selected the top four wicket-takers and two recent bowlers of different types and from different countries.
Average comparison for selected bowlers
|Bowler||Career Avge||Home Avge||Away Avge|
Warne and McGrath have bowled with the same level of effectiveness home and away. For Muralitharan there is significant variation. Kumble, Harbhajan and Ntini have very significant variations. Please note that I have selected Harbhajan and Ntini only to show the type of variation which can exist.
It took me quite some time to compile the CTD Home and Away values. Determining the values on a continuous basis and storing them in the match data base presented its own problems. Once I completed that I have re-done the BQI and this has come out very well now. I am not going to show the BQI tables now since more work has to be done.
I would give an example. In match no 1820, played at Christchurch between New Zealand and Sri Lanka, the BQI group was 5 for both teams since Murali's Ctd-figures were 657 at 21.96 and they also had Malinga and Vaas, very good bowlers. However Murali's figures comprised of 406 home wickets at 19.65 and 251 away wickets at 25.71. Once the Ctd-Away average was applied Sri Lanka went to Bowling group 4. New Zealand firmly stayed in group 5 since Bond had done reasonably well both home and away while Martin had a 15% variation between home and career. Only Vettori had done better away but he bowled very little in the match.
Now for Recent Form. This was again very tough work. I tried doing some short cuts, in flight, as I processed the match database. However that was not effective and fool-proof. Finally I bit the bullet and took the major step of incorporating the career details, match-by-match, into the Player database. This doubled the database size at one shot since I had to provide space for 220 matches. Ha! what is this 220. Well, Tendulkar has played 184 as on date and I have estimated that it would take him over 3 years to play more than 36 Tests and THAT is very very unlikely. Well, if that happened or Kallis played another 73 Tests, I will gladly go through another re-vamp. The advantage is that I have, for the first time, the player's entire career in a single record and can come out with many different types of analysis.
The Recent form work has come out very well. It is going to be very significant also since the form swings are widely varying. There is nothing gained by looking at absolute values. A 10-Test average of 20 for Sangakkara is a disaster, 35% of his career average, while the same for Vettori is around 65% of his career average. The following tables show the extreme values in Recent forms for batsmen.
Please note that the Recent form work is for the last 10 Tests, irrespective of location. I cannot very well do it separately for Home and Away since it might take players even 5 years to play 10 away Tests and that is too long a period. However I have done a minor adjustment, based on a suggestion from Sriram. Within these 10 Tests, I have done a minor tweak of 95% for home and 105% for away performances. Also remember that the recent form work has started after the players play 10 Tests or more.
In great batting form
Probably it looks as if I should do a separate article on Recent form. Vengsarkar had the best form anyone has ever had. During a 10-Test period during 1987, he scored at 302% of his average. His scores were 37*, 126*, 33, 61, 102*, 38, 0, 22*, 164*, 57, 153, 166, 96. Gatting's golden period was during England's golden period, 1985. Tillakaratne performed at 267.8%. Incidentally during this period, both Vengsarkar and Tillakaratne performed for more than 10 Tests at only slightly lower levels. Note the wonderful batting form exhibited by Mudassar Nazar during 1983 and Imran Khan during 1990. Imran was averaging better than many a specialist batsman at his peak.
It can also be seen that it is not exactly possible for the top batsmen who average above 50 to achieve these RF-Idx % figures since they would then have to have recent 10-Tests average of over 150 or so, not very easy.
In awful batting form
Let us take the other end. Nasser Hussain had the worst streak anyone has ever had. Ponting can take heart. His current run is far better than Hussain's whose scores ran 15, 16, 25, 10, 21, 0, 15, 8, 10, 6*, 22, 0, 0, 7, 0 retd, 23 and 5. Steve Waugh had a similar nightmare at the early part of his career in 1992. It is amazing that Botham carried a run of 8, 35, 9, 4, 37, 7, 0, 0, 16, 26, 1, 1, 13, 16, 1, 33, 0, 0 into the Headingley Test. And how he broke this barren spell, with knocks of 50 and 149*. Everyone knows about Dravid's recent barren spell. Here it is in black and white.
Thus it can be seen that the range of RF-Idx is ten-fold, 31.2 to 302.3, that too for established batsmen who have scored 3000 or more runs.
Now for the bowlers, the more important segment of Recent form analysis since these are the ones used in adjusting the BQI. The extreme values are given below.
In great bowling form
Lock's 10-Test period saw him performing at around 2.5 times his career average. His Test performances were 3/66, 2/38, 3/86, 1/29, 11/48, 3/25, 9/29, 11/55, 8/96, 3/39. Briggs was about 225% better. However see how quickly we go below 200%. This also gives a few not-so-great bowlers like Hooper and Edmonds chances to have their golden runs and move to the top of the Recent form table. Hooper, for a period, bowled like Muralitharan and Edmonds, for a while, bowled like CTB Turner. And Bailey was giving SF Barnes a run for his money !!!
Same as for batsmen. Tough for top bowlers to have a very low % since their averages are already low. For instance Muralitharan's best period has been during 2007 when he captured 89 wickets at an average of 14.62, still giving a RF-Idx % of only around 150%, not enough to even come in the top-10.
In awful bowling form
On the other side, Shastri had a horror run. He performed nearly three times worse. Intikhab had a similar disaster run. Look at Ntini's barren period recently. Sobers was bowling like a millionaire and Underwood like an out-of-form Sobers.
The Recent form adjustment is briefly explained below. The adjustments are done based on averages since that is the most stable and proven of all measures.
For good form, ignore if the RF-Idx is within 20% above the career batting average. If the RF-Idx is above 120% of career bowling average, then apply the adjustment factor which will vary from 0.80 to 1.00. The Ctd-x bowling average of the bowler will be multiplied by this adjustment factor.
For Lock, the adjustment factor is likely to be around 0.82.
For poor form, ignore if the RF-Idx is within 10% below the career batting average. If the RF-Idx is below 90% of career bowling average, then apply the the adjustment factor which will vary from 1.00 to 1.20. The Ctd-x bowling average of the bowler will be multiplied by this adjustment factor.
For Shastri, the Adjustment factor is likely to be around 1.18.
Thus the RF related adjustment factor for individual players varies between about 0.8 and 1.2. Let me recapitulate that we are looking at a player's recent form. It does not matter whether he achieves this at home or away. Also remember that these are extreme values.
Let us keep in sight that these are individual bowlers' recent form indicators. When the BQI is determined, first the individual bowler's values are adjusted and then the final BQI compiled. Thus a single BQI is a composite of 4/5/6 bowlers, some in good and some in indifferent form. This leads to a lot of evening out. The team itself will carry a significant adjustment value on either side of 1.00 only if it happens that most of the bowlers are in good form or most of the bowlers are in poor form. This does not happen often. The final innings level adjustment, for the first innings, varies between 0.86 and 1.11. Second innings has a similar range. These innings, which are very illustrative and illuminating examples, are summarized below.
Two innings with extreme Recent form adjustment values
Match Id: 0834
England vs Australia.
England RF-Idx for innings was 0.86.
4 out of 5 bowlers were in great form.
Match No: 0774 Year: 1976 India vs West Indies. India RF-Idx for India was 1.11. Venkataraghavan-120%, Bedi-137%, Chandrasekhar-128%, Madan Lal/Amarnath-100% (They had not even played 10 Tests). All 3 main bowlers were in poor form.
The sanctity of the word "Recent" in Recent Form will be maintained, to the extent possible. If the Recent period extends beyond 2 years, due to injuries, non-section or external factors like War, it would not be considered. However I am not able to confirm that this can be done because it is quite tricky to decide where to draw the line. The impact is likely to be infinitesimal
Now to apply all these rather complex adjustments and come out with the BQI. The revised ranges are given below. These values have changed significantly because of the various changes implemented. Hence the grouping also has changed. The BQI values are capped between 15.0 and 60.0. The distribution has a mean of 35.67 and a Standard Deviation of 7.75 which works out to a Coefficient of Variation of 0.217, indicating a very balanced distribution.
Summary of BQI Grouping
15.0 - 27.0: Group 5 - 1002 (13.7%) Amongst the best of all time
27.0 - 32.0: Group 4 - 1657 (22.6%) A very good attack
32.0 - 38.0: Group 3 - 2085 (28.5%) Good attack
38.0 - 45.0: Group 2 - 1577 (21.5%) Below average
45.0 - 60.0: Group 1 - 997 (13.7%) A poor attack
To download/view the document containing the complete BQI / PQI tables please click/right-click here.
In the next article I will cover the Pitch Quality Index in depth.
Anantha Narayanan has written for ESPNcricinfo and CastrolCricket and worked with a number of companies on their cricket performance ratings-related systems