Introducing Ball Progression for the SPFL Premiership
The generosity of Scottish football fans earlier this year resulted in a successful Modern Fitba fundraiser that allowed us to purchase Scottish Premiership data from Ortec Sports. Ahead of the 2019/20 season we’ve been busy testing out our new toys and what metrics we can create with them. So far, we’ve been able to re-introduce Expected Goals and Expected Points models, while also being the first site to publish an Expected Passing model and PassSonars for Scottish football.
Another advanced metric that has become more common in the bigger leagues over the last few years is ball progression: measuring which players are most adept at moving the ball towards the opponent’s goal and into dangerous areas, be it through passing or carrying the ball at their feet.
Such information is used to create non-shot expected goals models, i.e. measuring the likelihood of a goal being scored based on where and how a team has held possession, while other analysts simply use it as a measure in itself; how many times has a player moved the ball into a certain location?
While Modern Fitba are planning a non-shot xG model of our own, it’s the latter metric I’ll focus on in this article and especially the concept of ‘deep progressions’: where the ball is moved into the most dangerous areas of the pitch.
So how do we calculate and define such a ‘progression’? With Ortec data we have the exact location of where each pass and ball carry started and ended, and whether they were successful or not.
I’ll define a progression as any successful pass or carry that takes a team 10 metres closer to the opposition’s goal, while also moving at least 10 meters up the pitch vertically. So this isn’t simply about moving the ball ‘up the field’ but also involves moving the ball towards the goal: a long diagonal pass from the centre to one of the wings might not have moved a team’s possession 10 metres closer to the opponent’s goal, even though the ball is 10 meters higher up the field vertically.
If we included progressions to any part of the pitch the overwhelming factor in deciding which player would come out of top would be their position on the pitch and the style of play of their team: It’s four Celtic centre-backs who have the most total progressions in the league, as they are often able to bring the ball out under no pressure in their own half while also playing in a team that value keeping possession of the ball and building up play from the back rather than going long quickly.
So I’ll focus on these ‘deep progressions’, where the ball has been moved more than 10 metres towards the goal into or within the final third of the pitch. Holding possession and moving the ball significantly towards goal in these areas will be one of the key targets for any football team, hence why we want to focus on them. I’ll also distinguish between progressions into the middle (defined as the width of the penalty box) and the wings.
Finally, by grouping together players who operate in similar parts of the pitch, we can more easily compare and identify players who stand out among their peer group. For example, central midfielders and (offensive) full-backs are in the prime position to be able to move the ball into the final third of the pitch, as they often receive the ball just in front of that part of the pitch. Whereas strikers - stationed high up in the field - will usually have much less room (and fewer teammates to seek out) ahead of them.
I’d argue that as a metric, ball progression is at its most relevant when applied to midfielders operating through the middle of the pitch; the ticking heartbeat of a side, responsible for moving their team up the pitch and into dangerous positions.
Here’s the results:
If you had asked Scottish football fans: ‘which midfielder in the Premiership is the best at moving the ball towards the opponent’s goal‘, then Callum McGregor would probably be a highly popular answer. It’s also correct: McGregor is second in the league among central midfielders for both deep progressions through the middle (3.9 progressions per every 90 minutes played) and up the wings (2.5 p90).
That such a guess is proven to be right by the actual numbers is something an analyst would be very pleased with. We call it ‘passing the eye test’: if what we pick up from watching games is also reflected in the data it’s a good indicator that the metric may be of real value.
It also means you can be confident that those players who are doing surprisingly well are genuine top performers in this area, perhaps doing their good work somewhat under the radar. With a big part of analytics being about unearthing value and marginal gains, trying to uncover such hidden gems is a key element.
While not a hidden gem, is Olivier Ntcham still slightly underrated (or underappreciated) within the Premiership? While he has been criticised for his consistency, within Modern Fitba we’re used to seeing Ntcham performing well on advanced stats, especially when it comes to chance creation.
Ball progression is no different. In fact, his numbers are very, very good. He tops the league – and not just among central midfielders - for deep progression through the middle (4.0 p90), but it is his ability to utilise the wings to progress the ball closer to the opponent’s goal which really stands out: at 3.6 progressions p90 he is almost 50% better than the second best player in the league (McGregor).
Ryan Jack is the first non-Celtic player on the list for progressions through the middle, a very stark contrast to his teammate Ross McCrorie: of all the central midfielders in the Premiership season with 9 or more full games played, he has the fewest deep progressions through the middle, at 0.5 p90. McCrorie is also second last when it comes to total deep progressions, with only Murray Davidson scoring a lower number.
Another interesting name that pops up high on the list is Gaël Bigirimana. The Burundi international has hardly played for Hibs since his transfer from Motherwell in January, but he keeps showing up well on our advanced passing stats, most recently when Matt Rhein introduced Expected Passing for the Premiership last month.
Bigirimana is 6th when it comes to total deep progressions, the highest ranked player outside the top 6 (or who played the majority of their games for a bottom six club).
Which leads nicely into another way we can shape and study this data. Within football analytics it’s become common to adjust certain metrics based on the amount of possession a team hold. A team with a large amount of possession will almost always have more passes and commit less tackles than a team with low possession – so looking at what players do per every minute their team hold possession can help compare players across teams with different playing style and of different quality.
The other side of the argument is that if a team holds a high amount of possession, it’s usually because of the simple fact that they have better individual players, so this shouldn’t affect how a metric is viewed. My view is that possession adjusted data, especially when it comes to a metric such as ball progression, would be a good way of identifying and highlighting talented players at clubs who might not see as much of the ball as players at ‘better’ clubs.
Below is the same graph as above, but showed in a slightly different way: deep progressions in the middle and wing per every minute that player’s team held possession of the ball in a game.
So what has changed? Ntcham and McGregor are still the top two but Bigirimana has now moved up close to them. When it comes to deep progression into the opposition’s half, he’s the 3rd best in the league when adjusted for possession. Another interesting name is St. Mirren’s 20-year-old midfielder Cameron MacPherson. While only playing just over 11 full games this season he’s been very effective in them: he’s got the second highest deep progressions in the league down the wings per every minute of team possession. These are highly impressive numbers. It’ll be well worth keeping an eye on MacPherson’s development over the next couple of seasons to see if he can keep producing such great numbers in a crucial area for a midfielder.
Throughout next season, Ball Progressions will be part of Modern Fitba’s new set of advanced stats used to analyse the teams and players of the Scottish Premiership. In this first outing, it has both confirmed the quality of some high-profile players such as Callum McGregor and Olivier Ntcham, while also highlighting the more unsung performances of Gaël Bigirimana and Cameron MacPherson. In future articles I’ll look closer at players in other positions on the field and their ability to progress the ball into the areas that matter the most.
*Thanks to Seth, Jack and Matt who helped develop the formula to calculate distance to goal. I’m very grateful for them having bigger brains than me.