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Data analysis - shaping football [and Bolton] as they enter new territory

Guest writer Liam Hatton conducted an interview Bolton Wanderers' Head of Analytical Development, Brian Prestidge. The conversation covered the future of data analysis in sports and what it means for Bolton Wanderers.

Charlie Crowhurst

"I’ll start with the first and most boring aspect which is just looking after the department, where we get the whole financial meetings." Brian Prestidge summed up the way football has advanced in today’s game with that one line. Yet his job is so much more interesting than he lets on, whether he likes to admit it or not.

Prestidge is the Head of Performance Analysis at Bolton Wanderers, where they are quietly becoming one of the best teams in the country in that regard. Well recommended and respected amongst fellow peers, they have forged links with the likes of Manchester City and West Bromwich Albion to name a few.

In addition, Prestidge has spent time at a conference in New York over the last week, with a specific aim towards data analysis. Guests included new Manchester United manager, David Moyes, and NBA stars such as Amare Stoudemire.

So with the news of Dougie Freedman and his Bolton Wanderers team looking to modernise their player recruitment and data analysis (or scouting for those old fashioned people), there is obvious change behind the scenes as the club are still moving on from the Owen Coyle era, and it should come as no surprise that Prestidge is at the head of this new-look department.

I caught up with Brian in November of last year, and whilst the Trotters have gone through recent hardships, including countless managerial changes, the increase in debt year by year, relegation from the Premier League, and the agonising final day drama of missing the playoffs last month. One thing that has remained constant and gained admiration has been the Performance Analysis program run behind the scenes.

What data is relevant?

"Using products like ProZone, you can see relationships and interrogate those relationships, two clicks can create a starting base to find out what relationships are key", said Prestidge. However, the complex and detailed nature doesn’t rest firmly on ProZone’s shoulders, looking at the data ahead of games isn’t enough, as much as knowing how much of that data is actually relevant. "Even if you cut it down and just understand a small portion, that helps more than taking all of these numbers and trying to analyse a bigger sample."

There’s no doubt football has changed dramatically in a short period of time, the game is now reinforced by the monopolised nature, and is subsequently determined by how well teams are backed financially. This leads into minimal room for error, especially for clubs such as Bolton who have marginal funds and the constant pressure to land the right faces.

Prestidge realises that because of this the recruitment system in place needs to get it right, especially as his data analysis also links into that same process. Before bringing an individual aboard factors have to be accounted for, "How do they fit into your system? Do certain statistics matter such as pass completion? Or maybe these are irrelevant factors," Prestidge said. "Statistics don’t tell the whole story, you can’t base your analysis solely on the number of passes a game. Are these all relevant to first of all playing within your team and style? And secondly do they help us to create chances?"

The risk of change.

Beyond knowing how much data is equivocal, there are then questions surrounding how to use it to a team’s advantage. Knowing where the ball is travelling to and when obviously helps that case, and as Prestidge says, "you stop it at the source, before it gets to the key player". The lines are blurred between knowing whether you focus more on the main trends, or placing extra emphasis on stopping the opposing team’s key players – "It’s not always about being the strongest as it is using methods that work, we say that these are our strengths so we’ll use these on a particular day against a particular opponent."

As the analysis is adapted, there are other factors that sometimes can’t be helped, especially when that involves looking at data sets from different seasons. Whether that’s the transfers of players to other teams - "over one season we had over eight new first team players" - managerial changes, relegation and promotion, formation changes and a modification in attitude are prime examples. Prestidge laments those potential problems, "One season doesn’t involve much change, but looking at sets over different seasons affects our analysis to a large extent."

So, do the statistics stand up on their own?

Moving beyond my interview with Brian for a moment, and expanding more on what he said about raw data and how it’s looked at in a variety of ways, I decided to try some analysis of my own. It’s important to note that most raw data isn’t relevant in every aspect, but when said data is narrowed down therefore focusing on one particular part, the bigger picture is sometimes readily available. How the data is perceived is of paramount importance, as CNN notes "you’re not just getting more information, you’re getting a new dimension of understanding."

The interpretation of this particular date is courtesy of a scheme set up by Manchester City (MCFC Analytics). This allows any user to receive data from every game and interpret it however he/she wants to, a must for students or even fans of the game


S = Successful
U = Unsuccesful


The above table effectively tells you how successful each Manchester City player’s passes were in the defensive, the middle, and the final third.

Every single one of Joe Hart’s passes to the defensive third were successful. This is purely a given as he constantly resides in that area, (therefore his passes will most probably be short and relatively easy). However his passes to the middle and final thirds were less successful. This is likely due to the fact that the distances for the passes in the middle and final thirds were longer and more opposing players were in close proximity, thus a higher chance of an unsuccessful pass completion.

The full back pairing of Pablo Zabaleta and Gael Clichy had an unusually high successful passing percentage in the middle third, this showcases their tendencies to advance forward and help aid the Manchester City attack. Whilst this shows positive results it can also leave them vulnerable when they have to track back and defend, it also indicates to other teams about their inclinations and weaknesses.


The former champions lacking that physical edge?

1) Aguero's win/loss duel percentage is a potential cause for concern, especially as he is deployed as the main goal threat for most games. This shows Aguero is taking on a lot of runs by himself, is this because of a lack of support or a continued eye for goal?

2) Barry and Toure see a great chunk of the battles in the middle of the park, Barry is highly successful whilst Toure is losing a lot of 50-50 challenges. This is both surprising and interesting because Toure is rated as one of the best in the world at his position, whilst Barry gains a lot of criticism for being pedestrian like. Regardless, both are key in building up transitional play from the back four to the forward line.

3) Clichy is perhaps the most underrated player in this City team (if that's possible). As seen in the previous graph his passes in the middle of the park were highly successful due to his ability to attack. But the duels that favour him whilst defending are equally if not more impressive, as this show his ability to stand up against pressure.

With just two pieces of free data that are readily available to the public, the results and trends made available are second to none. Data analysis shows how easy a team’s weaknesses can be spotted, exploiting that is another matter however. The resources available to the likes of Brian Prestidge at Bolton will be far more competent, and as Dougie Freedman and the analytical team obviously hold a greater knowledge and appreciation of data analysis therefore they’ll be able to introduce new concepts. But to say this type of analysis is a helpful tool and is becoming a huge part of modern day football is an understatement.

Impacting The Trotters.

The new set up in place is already helping Dougie Freedman close in on his selected targets, with former Norwich City full back Marc Tierney a formality, and ex Blackpool utility man Alex Baptiste nailed on according to Freeman himself. An early headstart in the transfer window is something the boss has put down to the changes in player analysis. It’s something Freedman has known throughout his playing and short coaching career, as he spent time with the AC Milan team in the past focusing on player analysis in detail.

"Gone are the days where you’ve got a bloke stood behind the goal with a flat cap watching players for the club and scribbling notes down on a notepad," Freedman was quoted by the Bolton News. "That might be how other people like to do it, but we want to come at it from a different way completely". The process has been there in the background for quite some time, and you could argue that it’s down to some ex manager’s ideologies that this line of thinking wasn’t brought to the forefront much earlier. Freedman continued by saying, "Brian [Prestidge] will be working very closely with Mark Leather and that will provide the basis of how we sign players, based on their physical attributes".

The recruitment and analysis model in place is taking inspiration from that of what David Moyes and his former club Everton implemented, the main reason Prestidge was in New York listening to Moyes this week.

Jen Chang from Sports Illustrated examined Everton’s model in detail, and how it’s been in place since Moyes’ first year as Everton boss. Chang also looks at how widespread data analysis has become, and how players are becoming more receptive of this compared to years ago, something which Brian agreed with. He went on to say how products like Pro Zone and Catapult help breakdown this data making it easier for players to understand what their particular assignments are. Fitness is a main concern also with Prestidge stating that, "the key thing is making sure players are physically conditioned, things can change with two games a week, especially in the Championship".

The moneyball effect?

This has become a seemingly global phenomenon, especially in the world of Major League Baseball, but as for Bolton [and football as a whole] this is not the case. "As much as people would love it to be it’s not an exact science, in regards to baseball and the moneyball effect it’s not the same thing". Prestidge continued by declaring Baseball revolves around hitting a ball and catching that ball, football introduces more differing factors. "As soon as you take a corner then there could be a free kick or a foul, every single movement in football can change the whole pattern of play and the outcome."

The future is bright.

Prestidge made note of a trickle down effect to the employees at the club. He placed particular emphasis on 'promoting from within the club' and making sure people are ready to step up when others leave. "You have to leave a progression, Lee Sargeson [who was part time before moving up] could move up into my role as I moved up a level. You don’t want to retrain and bring in others from outside, it’s about looking after the longevity of the club".

The realisation of sometimes needing to hire from outside is apparent however, as Prestidge himself was an outside hire from the University of Wales, Cardiff. "I spent a year in the academy before moving up [the year Big Sam left], when my boss Ed left to join Manchester City I stepped into his role. Most positions were filled from within apart from one who came in from the University of Wales."

As football grows and becomes more of a global juggernaut day after day, there are new procedures in place to help coincide with that growth. Internships and jobs are constantly becoming available, "We've got a link in with both UCLan and Nottingham Trent, who run a good Performance Analysis course", Prestidge noted.

"If you understand even a small portion of data extremely well you can start to build from there."

Right now data analysis is at that point, just starting to build, but the scary thing is that it's showing no signs whatsoever of slowing down.