Analysing the effectiveness of bowlers with the old ball, I think Fast bowlers should be used sparingly with the new ball, which should mainly be in the hands of swing/seam bowlers.
I was looking at the impact of the new ball in Tests, and how it varies by country*. The general trend is that once the ball is 20 odd overs old the pace bowlers get little help. But then Australia bucked the trend.
Enigmatic Australia. I couldn’t find a new ball benefit for pace bowlers, other than the first three overs.
If you knew nothing of cricket, and just went by the chart, you’d say overs 6-20 (average 37) are as hard to bowl in as any of the first 60 overs.
Why isn’t the new ball helping the bowlers in Australia? I think it’s because selectors pick fast bowlers who are best suited to the quick and bouncy wickets. Think Steven Finn rather than Chris Woakes. “Fast” bowlers are more consistent through an innings than other pace bowlers**. Here’s the performances of fast bowlers*** in all countries:
Figures 1 and 2 are very similar! Averages by over in Australia look just like those of fast bowlers generally. The pitches in Australia encourage fast bowling, so the graphs are basically the same. Putting it another way, the new ball effect looks small in Australia because most bowlers don’t rely on the new ball.
What about pace (not fast) bowlers? Contrastingly, they are deadly with a brand new ball, dangerous until the 20th over, but then rather ineffective – especially overs 60-80.
Pace bowlers are not a homogeneous group. From now on, my model won’t just look at spin vs pace, it will split pace bowlers into “fast” and “not fast”. The “fast” bowlers don’t need the new ball, but do get an edge in the first five overs as the batsmen aren’t set. Other pace bowlers get a boost through the first 20 overs.
Who should bowl and when?
A big question. The fielding team’s goal is to minimise the expected runs of the batting team. That means managing resources – 68% of innings last over 70 overs, so four bowlers are going to at least three spells. When should those spells be?
There’s a point in the innings when a fast bowler becomes more effective than a swing bowler. It depends on the ground, the relative quality of bowlers, and the weather.
On an average pitch, the crossover is in the fifteenth over. If you had an equally talented attack of three swing bowlers and one fast bowler, the fast bowler should be held back until after the crossover, and bowl as much as possible with the old ball.
The trend of the above charts (since 2005) still holds true: current Fast bowlers average 4% more in overs 20-80 compared to overs 1-19. The equivalent figure for other pace bowlers is a whopping 19%****. You don’t want to make Medium-Fast / Fast-Medium bowlers use and old ball.
Please forgive the absolutes above. Of course, there’s no sudden leap between “Fast” and “Fast Medium” bowlers. And if the old ball is reversing then by all means pass it to the swing bowler.
But – I think this kind of analysis is important. It’s only by codifying and quantifying we can get closer to understanding the game. The assumptions and simplifications can be ironed out later.
What’s next? Once someone (maybe me, maybe you) has the data on how spell length impacts performance, and a reliable way of combining specific (head-to-head) and general matchups (eg. OS vs LHB), we’ll have a model for the optimum bowler for the next over. From there it’s a small step to planning optimum bowlers for the next session.
Footnotes
*Methodology: Pace bowlers (career average under 35) against batsmen (career average over 30). That way we’re avoiding the effect of cheap wickets at the end of the innings, and just looking at the real contest between bat and ball. All my ball-by-ball data comes from cricsheet.org.
** Fast bowlers should be about as quick later in the day. Two bits of evidence for this- firstly the academic research implies it (link and link). Secondly the speed data for Jasprit Bumrah and Olly Stone from India v England, 2021.
And, because it’s interesting I’ll give you two more footnotes to this footnote:
- According to this there is a speed decrease of around 4kph from bowling in heat on consecutive days
- Jofra Archer had a tendency to decrease in speed through the innings in India. He might not be like other fast bowlers. That’s not necessarily a criticism – being able to switch from RF to RFM might allow him to bowl more overs.
***Note this is 20 Fast bowlers, among the leading wicket takers of the last 20 years. Not quite the top 20, as I tried not to have too many from one country (Australia).
****Based on cricinfo’s classification of bowlers (F, FM, MF). Only includes balls when bowling to batsmen who average over 30. The population in question are the 25 leading pace wicket takers from March 2019 – March 2021.
Red Ball Data 
Interesting analysis. Thank you. Teams like Australia, South Africa, and England often opt for three or four fast bowlers compared to one or two spinners. Spinners take nearly all of their wickets after the 20th over. if you can find two spinners that average close to 30, is it worth having a bowling attack with two pace bowlers and two spinners. You might have your pace bowlers bowl long opening spells, maybe even 10 overs each, before having the majority of overs 20 to 80 being bowled by spin. If Australia had two Nathan Lyons, and played just two pace bowlers, would this result in teams being bowled out, on average, for lower totals?
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Thanks!
It might work in theory, but in practice your opponent would shift the best players of spin slightly down the order and make hay for 60 overs out of 80.
Suppose what I’m saying is that if opponents expect the tactic, they can easily counter it with selection and batting order.
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