JPL Shooting Stats & More after Gameweek 5

As we head into the 6th weekend of the Jupiler Pro League, I take a look into some basic statistics and infer how well the teams have been playing.

Shot Matrices

Dominance

Firstly, I look at the JPL team's "shot-dominance" – all credit due to Ben @experimental361 for this concept – by comparing the shots a team takes and faces, per game. 

• Standard has overall "shot supremacy" in the JPL so far: far outshooting their opponents and facing the lowest number of shots per game.   
• OHL’s defence has been the busiest, Standard’s the least busy. 
• Genk & Zulte both outshot by their opponents. Genk has the more over-worked defence of the 2, but Zulte is hovering close to the overworked territory. Both teams have top-6 aspirations – both need to limit their opponent’s more, it would appear, in their bid to do so.

Efficiency

"Shooting efficiency" (again, hat-tip Ben) is defined by the number of shots taken to score one goal. The rule-of-thumb being: 'the fewer the number of shots a team must take to score 1 goal, the higher their level of shooting efficiency, or, the better they are in front-of goal'.

• Ostende – the league leaders – have been clinical in front of goal needing roughly 6 shots to score 1 goal, which when they take over 13 shots per game, on average, implies a high return. 
• But it is Waasland Beveren, the second-highest goal scorers in the JPL, that are the most efficient at turning their shots into goals, despite taking a below-average number of shots per game.
• At the other end of the spectrum, Gent and Charleroi are so far struggling to convert theirshots into goals as well as teams further up the table are.

Defence

To assess the effectiveness of a team’s defence, we approximate by comparing the number of shots a team faces per game to the number of shots it has faced per goal conceded. Good defences limit the number of shots taken by the opposition as well as limit the number of goals they concede.

• What immediately catches your attention in the chart above is the extreme outlier: Gent. The Buffaloes have by far the most effective defence at dealing with shots in the JPL. They limit their opponents to about 10 shots per game (only Lokeren and Standard face fewer), and have conceded a goal only every 25 shots from their opponents’. 
• Standard face the lowest number of shots per game but have the third leakiest defence in the JPL. 
• Anderlecht’s defence also strays into ‘leaky’ territory despite facing the fourth lowest number of shots per game in the JPL. 
• At the opposite end of the x-axis OHL’s defensive frailties are fully exposed by this chart: they are overworked and leak goals.

Possession Game

I compare a team’s average possession statistic to their shots on target ratio (SoTR), which measures one team’s share of the sum of their & their opponent’s shots on target.

• The chart generally shows that the teams higher up the league have higher possession statistics as well as higher SoTR values. The exceptions are STVV and Zulte, which both have SoTRs than 0.5, but tend to have less possession of the ball in their games.
• Standard has the highest SoTR in the League at 0.66, translating to: 66% of the total shots on target in their games, eg if there are 15 shots on target in a game, Standard had 10, their opponent had 5. 

What's Luck Got To Do (got to do) With it?

Who need's luck when skill has spoken? Asides from just typing the worst pun on Tina Turner's classic in history, I try to assess the 'luck' JPL teams have had thus far. To do so, I turn to the PDO (credit due to James Grayson) vs. SoTR, or the 'good/lucky', matrix. PDO is the sum of shots percentage – which is the percentage of shots on targets that are converted to goals – and the save percentage – which is the percentage of an opponents’ shots on targets that are not converted to goals. PDO measures luck, averaging to 1000.

• STVV and Ostende are riding high on luck so far, with PDO values in excess of 1100, which is down to both teams scoring a high number of goals from a relatively low number of shots (than compared to, say, Anderlecht, Club Brugge & Standard, and to a lesser extent, Gent & Charleroi).
• Gent’s above average PDO is more down to their high save percentage & the stellar performances of Matz Sels. 
• Standard look to be due for a change in their fortunes some point soon. Whether or not that will come Sunday afternoon when they visit Club Brugge in what looks to be the most exciting fixture of the JPL so far this season, will be fascinating to see. 

Thanks for reading, I appreciate any feedback on how to improve. Cheers, Charlie.

Lowzer's Low Country Revue: Skill or Luck in the Belgian Jupiler Pro League at its halfway point...

The JPL has 16 teams. After 15 league matches the league is roughly at its "half-way" point. After 30 matches (ie after each team has played all other 15 teams home and away) the league then breaks into to playoff mini-leagues (Wikipedia has a good explanation). So, I thought looking at the JPL at its halfway point would be a good point to start my analysis of Belgians top-tier football division...

Skill or Luck?

I used data from soccerway.com to construct PDO, a measure of luck, and shots on target ratio (SoTR), a measure of skill, for the first 15 matches. PDO is calculated as: [goals scored/shots on target] + [goals conceded/shots on target against]. SoTR is calculated as: [shots on target for/(shots on target for + shots on target against)]. The higher the PDO the luckier a team is, the higher the SoTR the more skilful the team is. (For more detailed explanations refer back here). 

As the key to the chart explains the top-6 teams after 15 games are in Green and so on. 

Observations:

1. Generally the teams have clustered quite closely in the chart according to their league position with the exception of...
2. Mechelen, a real outlier: not only did it register the highest SoTR out of all teams in the Belgian JPL but it also experience a way low PDO over the first 15 matches. Now, this could be due to crap data or it could actually be the case that they have been really, really unlucky to be behind Sporting Charleroi and Kortrijk who were ahead of them in the table. 
3. Not only were Lierse and Cercle Brugge unlucky - according to PDO figures - but they also exhibited low skill, although Westerlo had the worst SoTR in the league.

Kortrijk and Sporting Charleroi are now in the top-6 of the league, Genk and Lokeren have fallen out of the top-6. However, to test this PDO vs. SoTR "model" as something with predictive power is probably not wise, instead it is a nice catch-all for what has happened.

AFCON 2015: Deserving Finalists, Skill Overcame Luck, and Luck Ran Out

Cast your mind back to one of my earlier posts on the 2015 Africa Cup of Nations where I used statistics to look at the skill and luck teams had in the group games. According to these stats, 6 of the Quarter-Finalists had benefitted from a lot of luck in the group stages. This came from my PDO vs SoTR chart: 6 of the Quarter-Finalists had PDO values of over 1000. 

Now, if you recall PDO is a measure of luck - the higher the number the more the luck the team has had. You arrive at a team's PDO figure by adding the percentage of goals scored from shots on target, to the percentage of goals conceded from shots on target against them. More broadly, the score percentage and the save percentage. The SoTR - Shots on Target Ratio - is the proportion of shots on target a team has of the total number of shots on target by the two teams. The higher this number is, the more skill a team has as it indicates they dominate the number of shots on target.

For reference, I bring back the PDO vs. SoTR chart from the group stages below. The chart clearly shows that Ghana and the Ivory Coast exhibited the highest skill - as indicated by SoTR - in the group stages of all the Quarter-Finalists (those teams with a Gold or Silver icon beside their three-letter country code).

This chart got a bit of love on Twitter in the past couple of days as it shows that despite a limited sample size (16 teams competing over the course of 24 matches) the SoTR (Skill) PDO (Luck) comparison yields some intuitive insights as to why teams succeed and/or fail. Additionally, the simple fact that there are no "lucky" teams - as shown by PDO, anyway - in the final shows that using this chart has some power in explaining things in this particular tournament.

Again, this is a small sample of data, and it must be stressed that Ghana faced, in Guinea and Equatorial Guinea, two massively inferior opponents in the knockout stages. The Ivory Coast have overcome bigger challenges to get to the final, so it will be an interesting one to watch. If, the skill levels (SoTR) continue to hold some predictive power - if I could call it that? - Ghana looks like the winner.

I've said it before. I'll say it again: I can't bloody wait for this final!

Further Analysis of the AFCON 2015 Quarter Finals: Luck must run out, or does it?

In my last post I talked about how skill and/or luck helped the quarter-final victors take their spoils.

In this post I am looking at another chart to explore the topic from another angle.

The chart I have made looks at PDO (Luck) of the teams playing in the quarter-finals of the tournament. It compares their group-stage PDO to their PDO statistic from the quarter-finals. Of course, this is imperfect as a comparison because the group stage PDO is over 3 games whereas the quarter-final PDO is from just one. However, the comparison is insightful as it shows that of the 6 teams with PDOs of over 1000 in the group stages, 4 were eliminated in the quarter-finals: Algeria, Congo, Guinea & Tunisia.

PDO indicates luck. Luck is subject to the laws of gravity. In short, it is possible that those four teams' luck ran out in the quarter-finals. Spare a moment to sympathise with Tunisia all the same.

Interesting to also note how 'lucky' the Ivory Coast and Equatorial Guinea were in the quarter-finals when thinking about what may happen in the semi-finals... As I said before, I think the counter-attacking performance of the Ivory Coast was excellent and, overall, deserving of victory. Furthermore, the Cinderella-story of Equatorial Guinea in front of their home crowd is a force to be reckoned with.

AFCON 2015 Quarter-finals: Deserving Winners or Unlucky Losers?

This weekend was a mammoth weekend of football which obviously means mountains of potential writing material. However, since my recent focus has been on the Africa Cup of Nations tournament, it seems only fair (and logical) to continue in that vein. (And, the less said about Saturday's new-firm semi-final at Hampden the better...)

In my last post I discussed my observation a seemingly large number of goals have been scored in the last 30 minutes of these games. It makes sense, of course, as a knock-out cup tournament like the Africa Cup of Nations is all about the elimination of teams until a winner is crowned. Naturally, teams will push more in the dying minutes as their survival in the competition depends on it.

Luck or Skill?

Another theme of this tournament I have tried to explore is what role luck plays compared to skill. Work done by the excellent James Grayson using English Premiership team-level data has shown that even in leagues, and over time, metrics such as percentage of shots on target or percentage of shots saved boil down to luck much more than skill.

Using data from the bbc football match summaries, I graphed team skill and luck from the quarter-finals. I calculated a team's Shots on Target Ratio as a measure of skill and PDO as a measure of luck. The chart** is below:

Reminder: PDO (Luck) centres on 1000 and is mean-reverting. What this means for the purposes of this explanation is that teams at the higher-end of PDO have had more luck on their side than the teams on the lower-end of PDO. Additionally, we would expect PDO to converge on 1000 over time.

According to the PDO figures in the chart above, the Ivory Coast and Equatorial Guinea were luckier than Ghana and the Democratic Republic of Congo (DRC) were to be victorious in their respective quarter-finals. Ghana, for example, did not allow Guinea a single shot on target in their game and made it look easy. The DRC made a truly inspired comeback against Congo scoring four goals in slightly over 25-minutes. But they also shot nearly double as much as Congo did (21 to Congo's 12).

Hard luck or good tactics? Or, something else?

So, I sat there thinking about luck and skill...

After watching the Ivory Coast manage to beat Algeria 3-1, I thought it would be incredibly difficult to use any figures (apart from goals scored, obviously) to prove that Ivory Coast were deserved winners. Algeria seemed to dominate the pace of play, and seemed to be a much stronger team. Additionally, Ivory Coast looked very shaky in defense.

However, Herve Renard - the Ivory Coast boss - made an insightful comment about how he arranged his players tactically to overcome the individual strengths of Algeria, a team he considered the 'best in the tournament'. He told the BBC:

"We needed to be very well-organised and try to counter a team who are very strong individually." (emphasis my own)

In the same interview, Renard explained he thought Algeria were much better on the ball and going forward, but he set his team up specifically to make the most of the pace of the likes of Gervinho and Max Gradel to supply Wilfried Bony on counter-attacks. And, it worked.

Algeria themselves played a different kind of game to how they played in the group stages: they had more possession and shot more. In the group stages they averaged under 50% of the possession in games. In this quarter-final they had 60% of the possession. In the group stages they took around 7 shots per game (on avg.). In this game, they took double that, 14 shots. But Ivory Coast had all the right answers to Algeria's change of style. And, Ivory Coast had Wilfried Bony to thank who scored twice and drew Algerian defenders to foul him four times. Algeria could have done with a presence like his in their attack...

In the Tunisia-Equatorial Guinea match, however, I think poor refereeing luck played a huge role in assisting the hosts progress to the Semi-final. An extremely soft penalty awarded to Equatorial Guinea in second-half stoppage time seemed to be so unfair on Tunisia. I think the image below says much more than my words can...

I think this @AP image pretty much sums up the Tunisian mood right now... #AFCON2015 pic.twitter.com/urAwWRxF7k
— Joe Crann (@YesWeCrann) January 31, 2015

Dominance in the Quarter-Finals? Or, was it really luck?

I also wanted to look at the games in another way so I looked at the shot-dominance in the quarter-finals. Recall from my earlier post when I dived into a preliminary statistical sweep of the group games that the sweet-spot of the graph below is the bottom-right corner. This is where teams take many shots and limit the number of shots taken against them. In this corner is Algeria and the DRC. Now, from the PDO vs. SoTR chart above we already established the DRC ran out deserved winners. And, from what Renard said about his tactics against Algeria we see that the counter-attacking style of play is not well accounted for in these charts. 

chart concept from Ben Mayhew of experimental361.com

An interesting part in the chart below is how closely matched Equatorial Guinea and Tunisia were over the course of 120 minutes - at least in terms of shots. Again, it is hard for these charts to take refereeing decisions into account...

** Updated on 2/2/15 at 16:30 to include revised PDO chart