Developing New Metrics: Set Piece Delivery

Josh Hobbs looks at another novel metric generated by TransferLab.

One of the perennial problems using data to analyse football is the discrepancy that exists between those with the ability to manipulate data and those who understand what is taking place on a football pitch. Where data scientists will be able to build models or scrutinise the numbers, they may not know how to structure their models or implement their findings on the training ground. Equally, where football coaches will be able to break down the game into phases of play or recognise rehearsed patterns, they may not have the ability to make the data coherent in a way that helps them in their jobs.

At Analytics FC, we have attempted to overcome this problem by building a model which begins to interpret the raw data. Using our unique TransferLab algorithm–a Markov Chain model–we are able to take events that happen on the football pitch and ascribe them a numerical value which indicates how much an action improved that possession’s probability of ending in a goal (and just as importantly, how much it reduced the other team’s chance of scoring on the next possession).

For example, a player receives the ball in central midfield. At this point, the team might have a 1.5% chance of scoring at this point in the possession and also a 1% chance of conceding on the next possession. That situation isn’t very valuable. But if the player executes a dangerous through-ball into the final third, the team is now in a much better position and might have a 6% chance of scoring and only a 0.5% chance of conceding. The pass would be worth the difference in their team’s situation before and after it. 

The algorithm calculates every action and can therefore determine the overall impact a player has through all their actions and the impact is presented to clubs in terms of “Goal Difference Added” per 90.

The beauty of this approach is that it allows you to farm the data to find the sorts of actions that are creating value for teams and model your game-style to reflect that. If a certain pass into the box is proving a good source of value for a team, then the coach might want to think about ways to encourage those sorts of actions within the game. Suddenly, data and coaching are much more closely aligned.

In this series, we are going to explore some of these actions that add value to a team’s game:

Set Piece Delivery

The topic of set pieces has been at the forefront of English footballing discourse in recent weeks. This is, of course, due to the fact that Gareth Southgate omitted James Ward-Prowse from his final England squad for the Euros.

The Southampton captain is known as a set-piece specialist, and considering that England scored the majority of their goals from set pieces in their run to the semi-finals of World Cup 2018, the theory goes that Southgate had to pick him. However, even in an expanded squad of 26, Southgate saw fit to leave him out. 

Whether that is the right call or not remains to be seen but one thing that we can’t argue with is the importance of set pieces in modern football. Set pieces have always been a weapon that teams with less productive attacking systems have utilised, with Tony Pulis’ Stoke City a prime example in English football. A team built on firm defensive foundations, featuring plenty of tall, athletic players will always be a threat when they can pack the opposition box and get dangerous deliveries in on a regular basis. 

Outside of English football, FC Midjtylland—one of the teams at the forefront of data analysis in footballhave established themselves as a regular title contender in Denmark as well as a competitor on the European stage by maximising their opportunities to score from set pieces. Their approach involves intensely drilled and innovative routines to get players free to attack the ball but it still requires excellent delivery into the penalty area to get the most out of these clever routines. 

With that in mind, the next custom metric from TransferLab that we will be looking at is Set Piece Delivery (Quality). As per all the quality based metrics, this gives players a rating based on how they contribute to their team’s goal difference through their set piece delivery. 

According to this metric—although James Ward-Prowse shows up very strongly amongst English players competing in Tier 1 Leagues in 20/21 (minimum 720 mins played)—England might already have a better set-piece taker in their squad than the Southampton midfielder:

Before going on, it’s worth acknowledging that Matty James, James Garner and Matthew Smith should not be appearing here as they were on loan in the EFL this season. They appear to have been picked up in the search due to the fact that they have now returned from their loans and the data provider is recognising them as Premier League players. 

As you can see, the top performer is West Ham’s Aaron Cresswell with Ward-Prowse coming in 3rd. However, between them is Leeds United’s Kalvin Phillips who impressed for England against Croatia in the group stages of the European Championships.

As you can see in the example above, the Yorkshireman strikes the ball in such a manner to deliver the ball with great pace and whip. Of course, at times he gets it wrong and hits the first man, as all set-piece takers do. But when he gets it right, his deliveries can be very difficult to defend against. 

It should be noted that Ward-Prowse’s sample size will be significantly larger than that of Phillips’ due to the fact that Raphinha was the primary taker for Leeds. If Phillips had taken as many set-pieces as Ward-Prowse, he may not have maintained his level of performance in the metric. However, Phillips will certainly be an option on set-pieces for England and in fact has been one of the first options for free-kicks and corners when he’s been on the field. 

Other players going to the Euros who featured on the list are Mason Mount and Jack Grealish. Between the three of them, England have proficiency in terms of set-piece delivery. In England’s opening game of the tournament, it was in fact Mason Mount who took England’s solitary corner with Keiran Trippier on free-kick duty. 

Who are the Best Set-Piece Takers in the Big 5 Leagues?

Moving away from international football, let’s look at who TransferLab rates as the best set-piece takers in Europe’s Big 5 Leagues (Tier 1 competitions in TransferLab). In this case, I am adding the filter of a minimum of 1000 minutes played in 20/21.

Nobody should be surprised to see Milan’s Hakan Çalhanoglu as the top performer here given that 6 of his 8 assists in Serie A came from set-pieces. 

Here we see him providing the ball for Theo Hernandez to head a stoppage time winner against Lazio. He also assisted another goal from a corner in this particular game and is a constant threat taking corners from either side, as well as from free-kicks. 

One of the younger players on this list is the in-demand Romain Faivre of Stade Brest. His performances in Ligue 1 have attracted interest from clubs higher up the division as well as in the Premier League. The 22-year-old Frenchman is a powerful dribbler and creator in open-play but is also a real threat from set-pieces. 

He takes free-kicks from all over the opposition half but the position he took the one in the example above from is his sweet spot. This is also the kind of area in which he likes to cross the ball from in open-play as he has the perfect angle to swing the ball to the back post for a runner to attack. If he is to move this summer, he’ll be improving whichever team he moves to in the set-piece department. 

Using the Metric in Recruitment

Of course, the aim of TransferLab is to aid in the recruitment process of professional clubs. With that in mind, we’ll use the metric in a scenario to try and emulate this. 

Let’s imagine we are part of a recruitment team for an English League One club. This club is in the market for a midfielder. They would ideally like them to be a good set-piece taker as they have plenty of height in the squad and have identified set-pieces as a chance to score more goals but they’re missing a quality taker. 

With the GBE system now in place for English clubs post-Brexit, we will limit our search to specific leagues. In the current situation we can assume that budgets will be fairly small so we will look in League One, League Two, the National League, Scottish Premiership and Scottish Championship. Additionally, we’ll filter for a minimum of 1000 minutes and a maximum value of £1m. In this case, age is not a major issue due to the short-term nature of many signings in the lower divisions, so there are no filters on age. 

Here we have the list of midfielders TransferLab recommends:

Looking into their profiles, some don’t show up well at League One standard according to the other metrics which are included in the ‘box to box midfielder’ profile. Those can be immediately discarded. 

One player who did stand out is Lincoln City’s Jorge Grant: 

The midfielder scored 13 times and assisted 8 in 20/21 with a number of his assists coming from set pieces. It seems that his contract is up at the end of June as well. Considering that he put up such an output this season, he’s highly likely to be in demand. This would be one to investigate further but it demonstrates how TransferLab can assist in identifying quality players to make real improvements to any professional team.  

Developing New Metrics

In this series, we will be covering a number of novel metrics we have developed using TransferLab’s algorithm. However, we can create any number of new metrics to determine whether certain in-game actions accrue or reduce goal difference in games.

Using the algorithm, we can assign a “Goal Difference Added” per 90 value to any on-field action that moves the ball from one part of the pitch to another and then compare players using these values.

If you have any ideas about potential metrics, do get in touch with us and we’ll see what we can do to implement them.

Analytics FC provides software and data services to entities within football looking to realise the gains possible from analytical thinking. We provide cutting-edge software solutions such as TransferLab, which helps improve and simplify recruitment decisions. To find out more about TransferLab and our other data services, or to find out more about us, visit our website.

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