Monday, 1 March 2021

The Changing Approach of Batsmen to the Nineties

Cricket always puts a lot of emphasis on milestone achievements and none more so than scoring a century. The television graphics always show the number of hundreds that a batsman has scored, there is always discussion about conversion rates of fifties to hundreds and it is always celebrated by a batsman when he reaches that milestone. Last week, I ran a poll on Twitter that asked which of two batsman - both with the same number of runs and the same average, but one with 43 100s and the other with 0 100s - would be perceived as the better batsman.



The results came out in favour of the player with more centuries as one might have expected. I will admit that I expected it to be even more in favour of player 2, but various alternative theories were mentioned that did explain why some people voted for the former. In reality, the two batsman were created by simply taking Virat Kohli's career innings, but for player 1, every century was replaced with him being dismissed on 99 and for player 2, he was dismissed on 100 (and a few extra runs were scattered around for player 1 to ensure the averages were the same). All that player 2 achieved was to scored one extra run in 43 innings, but he is perceived as comfortably the better player.

This brings us to the question of whether the considerable emphasis on the century milestone changes how batsmen approach batting when they are closing on that milestone. There is always mention among cricket traders of the idea of a century slowdown, where a player plays more risk averse in the nineties to give himself a better chance of reaching his century, potentially to the detriment of the team. It would be entirely understandable why players might react this way - as long as there is emphasis on the milestones when it comes to player evaluation and team selection, it is beneficial for an individual player to maximise their chances of reaching that milestone.

As a very simple first step in looking at what happens when players are close to their century, we can look at their average and strike rate when they are on a score of 80-89, 90-99 and 100-109 to try and identify any obvious changes. In this article, we will exclusively focus on 50 over cricket.


Across all 50 over matches in the past five years, we can see that both the average and the strike rate for batsmen drops when they move into the nineties. Interestingly, this might suggest that players both look to play slightly more conservatively, but that change could also lead to an increased chance of being dismissed. Once they reach their hundred, the average does increase a touch, but the most striking difference is the change in strike rate. It would appear that almost immediately after reaching their century, players really go on the attack.

So, on the whole, it would appear that there is a bit of an effect of the approaching milestone. The next thing to look at is how that varies across teams - do players from certain countries put different emphasis on milestones?  


Focusing on countries at this stage, we can see a few interesting things in this table. The majority of countries see a slowdown when players move into the 90s, although the drop for the West Indies in particular is notable. England, South Africa, New Zealand and Afghanistan are the countries that see a continued increase in strike rate as players move into the 90s and they also all see a significant increase in the average during that period.

The West Indies demonstrate the unfortunate pairing of a significant slowdown in scoring as players go into the 90s, combined with a much reduced average. Either West Indian players have a big problem with nerves as they approach their century or they change their style of play in a way that leads to an increase in the likelihood of being dismissed. India also see a reasonable drop as players close on their century, but their players are far less likely to be dismissed in this period.

Looking at what happens after the players reach their hundred is also interesting. Almost across the board, we see a fall in average after reaching the century - whether this is due to greater risk taking or whether players lose concentration after reaching the milestone can be debated - however batsmen from different countries attack differently. We can see that England, India, West Indies and South Africa batsmen really accelerate after reaching their milestone, although with varying rates of success. English batsman really look to attack, but we can see that the average falls dramatically, suggesting that they really take risks to up the run rate potentially to their own personal detriment. Conversely, we can see that there is no obvious rapid increase in scoring from Australian, Pakistan and Sri Lankan batsmen, who appear to revert to their scoring rates from the 80s, although that doesn't always appear to reduce the chance of being dismissed compared to the more attacking approach of other countries.

So, can we look at some of the individual players to try and spot players that really slow down approaching their century or players that continue to attack?


These are a selection of the players with the biggest increase in their strike rate between the 80s and the 90s. Top of the list is AB de Villiers, whose strike rate approaching his century is quite ridiculous, although that applies to his strike rate at all stages around the milestone. Having noted before that English batsmen do not appear to generally show a slowdown around the milestone, it is no surprise to see Malan, Morgan and Stokes all appearing close to the top of this list. England have had great success in ODI cricket over the past five years and maybe some of that is down to players being confident of their place in the team, so not feeling the need to play for personal milestones?


At the other end of the scale, we can see the players that show a big century slowdown. It is also noticeable how many of these batsmen return to a rapid scoring rate once they reach their hundred, suggesting the slowdown is a fairly deliberate decision to attempt to reach the milestone. For example, Rohit Sharma, one of the very best limited overs batsmen, scores at 133.5 during the 80s, before slowing right down to 92.9 during the 90s. Once he reaches his century, he immediately returns to scoring at 131.5, almost exactly the rate he was scored at in the 80s.

Ultimately, this slowdown in the 90s might not have too much of an impact in the bigger picture. Taking Rohit Sharma again as the example, the change in SR means that he is expected to spend around 10.8 balls to score the 10 runs to take him from 90 to 100 rather than 7.5 if he had continued at the same rate. Whether the difference of those roughly 3 balls actually makes an impact in the majority of ODIs can be debated - clearly in the tightest of matches, those balls may make the difference, but I'd estimate that the majority of ODIs do not come down to that sort of margin. However, it does give an interesting insight into potentially different views on milestones between different batsmen.

Wednesday, 17 February 2021

Using Machine Learning to Identify T20 Opener Styles

There is little doubt that getting off to a good start in T20 cricket, as in any format, is crucial to being a successful team. Teams often look to get their best batsmen opening to ensure that they face as many balls as possible in the shortened format. However, history will show us that there are several different types of successful T20 opener - Virat Kohli and David Warner play a very different style of innings than Sunil Narine, but given the right balance around them, there is little doubt that all three of those players are very effective opening batsmen.


I wanted to look at finding a way to identify these different styles of opening batsmen using a simple machine learning technique. The important thing here is that I am looking to identify the styles of opening batsmen, not necessarily the quality of the batsman. Whilst that may come through within some of the styles, that is not the direct purpose of this. A certain style of opener may work well in certain teams based on their particular balance of other players whereas another team may be looking for something different. If you have a team of big hitters, an opener that plays as more of an accumulator might be what you are looking for to provide the stability for those other hitters. If you have accumulators in the middle order, you might want a more aggressive opener.


To achieve this, we will use K-means clustering. I will not go into the details here, but at a basic level, this simply looks to find groups in the data. For the data used, I took every player that had opened the batting in at least 10 innings in a decent standard T20 league (IPL, Big Bash, T20 Blast, PSL, CPL, BPL, Super Smash and internationals) since the start of 2018. For players that have batted in multiple positions, I only took their stats for those matches where they opened. This gave us a dataset made up of 128 batsmen. So, let's take a look at what we got from the algorithm.



Each cluster is represented by a different colour, the shapes mark the boundaries of each cluster and each cluster has a central point that represents it. We can see that we have six different clusters, although there is some overlap between three of the clusters. Hopefully we can see some similarities between the styles of the players in each cluster.


Cluster 1 (The Power Hitters)



Players: Sunil Narine, Ed Pollock, Rahkeem Cornwell, Moeen Ali and Finn Allen

The first cluster represents the pure immediate power hitters. There are only 5 players in this cluster, but the most identifying feature is their incredible strike rate right from the very start of their innings. Their innings do not necessarily tend to be the longest, but they are not going to waste any balls, they have the power and the freedom to find the boundary regularly and they can get your team off to a blistering start, although you may also lose early wickets.


Cluster 2 (Powerplay Specialists)



Players: Jason Roy, Parthiv Patel, James Vince, Usman Khawaja, Suryakumar Yadav, Liton Das, Joe Clarke, Adam Rossington, Steven Davies, Neil Broom, Neil Dexter, George Worker, Mark Cosgrove, Afif Hossain,  Ken McClure, David Lloyd, Junaid Siddique, Tim Seifert, Johnson Charles, Sam Heazlett and Mehidy Hasan

The obvious feature of the second cluster is their struggles outside of the powerplay overs. They consist of players that are relatively capable of picking the gaps during the powerplay as shown by a reasonably good fours percentage and a solid strike rate during this period, but lack the power to really push on once the fielding restrictions are relaxed. Having these players in your team is not a major problem, but you do run the risk of a real slowdown once the powerplay is over.

Cluster 3 (Attacking Openers)


Players: Jos Buttler, Aaron Finch, Colin Munro, Alex Hales, Phil Salt, Ben Stokes, Tom Banton, Mayank Agarwal, Luke Ronchi, Mohammad Shahzad, Chad Bowes, Graham Clark, Adam Wheater, Anton Devcich, Adam Lyth, Josh Inglis, Richard Levi, Johann Myburgh, Paul Sterling, Zak Crawley, Wriddhiman Saha, Hamish Rutherford, Ben Duckett, Rilee Rossouw, Miles Hammond, Aneurin Donald and Max Bryant

This is a cluster of attacking openers that are able to sustain that approach. They are certainly not quite as outwardly aggressive as the power hitters, but they are able to start attacking early in their innings and sustain that outside the powerplay. It is no surprise to see plenty of players in this group that would be considered as very good T20 openers that are capable of big scores. They may not necessarily have the range of shots to crank up the strike rate to insane levels, but they are very capable of starting well and continuing to score quickly once the fielding restrictions are relaxed.

Cluster 4 (Poor Openers)


Players: Shaun Marsh, Faf du Plessis, Hashim Amla, Andre Fletcher, Michael Klinger, Max Holden, Michael Pollard, Dom Sibley, Tamim Iqbal, Sean Solia, Chadwick Walton, Chandrapaul Hemraj, Daniel Hughes, Marcus Harris, Ben Dunk, Dane Cleaver, Harry Swindells, Mackenzie Harvey, Anamul Haque, Ahmed Shehzad, Luis Reece, Chris Nash, Jack Edwards and Nic Maddinson

I know I said that the aim of this was not to make judgments on the quality of players, but this cluster has all the hallmarks of those that you do not really want to be opening the batting for your T20 team. They are very slow starters, struggling to find the boundary and tend not to have the power to push on once they are settled. They are capable of making decent scores, but they would often be the likes of 60 off 50 balls-type scores that look at and think they are likely to be match-losing innings given the circumstances, regardless of what the commentators may claim.

Cluster 5 (The Accumulators)


Players: Virat Kohli, KL Rahul, Quinton de Kock, David Warner, Shikhar Dhawan, Babar Azam, Matthew Wade, Tom Latham, Stevie Eskinazi, Tom Kohler-Cadmore, Devon Conway, Josh Philippe, Tom Westley, Ian Bell, D'Arcy Short, Daniel Bell-Drummond, Scott Steel, Marcus Stoinis, Luke Wright, Ajinkya Rahane, Imam-ul-Haq, Alex Carey, Rahul Tripathi, Joe Denly, Alex Davies, Davdutt Padikkal, Shubman Gill, Varun Chopra and Billy Godleman

The clear standout feature of this cluster is the average number of balls faced - the 25.5 balls is more than five more than any other cluster. These players are those that play long innings in this format and do it at a reasonable rate. They may not have the power to really go crazy, but they are good anchor players to build your power players around that will not prove too much of an issue until the late stages of the innings.

Cluster 6 (The Accelerators)


Players: 
Chris Gayle, Jonny Bairstow, Chris Lynn, Rohit Sharma, Martin Guptill, Brendon McCullum, Evin Lewis, Dawid Malan, Liam Livingstone, Kamral Akmal, Brandon King, Cameron Delport, Will Jacks, Glenn Phillips, Prithvi Shaw, Riki Wessels, Shane Watson, Sharjeel Khan, Lendl Simmons, Ambati Rayadu, Fakhar Zaman and Jake Weatherald

This is a cluster of players that can both frustrate and excite. Only cluster 4 start their innings slower than this group, but only the pure power hitters score faster once they have their eye in. They know that they have the power to clear the boundary when they get going and take their time early to ensure that they are seeing the ball well. This can lead to problematic innings if they are dismissed around the 10-15 ball mark, but if they bat long, you can be pretty certain of a rapid acceleration.

Team Structure

Each cluster has its distinguishing features and they each have their positives and negatives. As good as some of the players in group 5 are, ideally you might not want two openers of that style unless you have an outstanding bowling attack. The players in group 6 give you excellent upside, but if you had two players from that cluster, you run the major risk of getting off to a very slow start that could be fatal if you lose wickets at the wrong time. Group 1 will undoubtedly get you off to a rapid start, but you have to accept the fact that you are also likely to lose early wickets.

Ahead of writing this, I asked around on Twitter as to who people considered to be the 'best' T20 opening batsmen in recent years. The four most mentioned players were KL Rahul, Jos Buttler, Chris Gayle and David Warner - all very valid answers. However, the most interesting aspect of that is that these four players fall across three different clusters, further showing that the style of opener alone on the whole does not make a batsman 'good' or 'bad'.

Knowing the different types of opener allow you know how to structure the opening pair and the rest of your team. Knowing the quality of players within each of these styles clearly requires a different way of analysing the data though. Whilst Virat Kohli and Billy Godleman are classified into the same style of play, nobody would argue that Kohli is not a far superior player. However, the balance of styles within a team is crucial and you could actually weaken your overall team by just crowding in the 'best' players if their styles do not mesh well within the greater team structure. This is something that it is worth considering for the IPL teams ahead of tomorrow's auction.

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