European Soccer: Goals to xG Performance
*This dashboard and page were designed for a desktop or tablet view and were, apologetically, not optimized for mobile.
Data Source: FiveThirtyEight
Github Repo for data transforms
In soccer analytics, expected goals (xG) are the sum of all the goal probabilities for every shot, and they serve as a fantastic measure of how a team or player creates or concedes goal scoring opportunities. If you compare them to the number of times they actually became goals, you can see which teams are over- or under-performing relative to the number of quality chances they are creating or conceding. Mike Goodman, soccer analytics writer at the late Grantland and then later at StatsBomb, lays out here very succinctly the strengths and limitations of xG as a metric:
To boil it down, the “very good” part is that what your xG per game across a whole season conveys is how often your team put themselves/were put in a goal-scoring/-conceding opportunity, and how often other teams score/concede from chances like that. Thus, comparing actual goals to xG is, in essence, posing a simple question: are you running hot or cold relative to the “average” team.
The not so “very good” part is that deciphering this performance relative to average so as to either replicate it or improve upon it is, like so many things in life, chock full of risk and uncertainty. Put plainly, it’s not straightforward to parse out what change in the performance you are getting is due to things you can (try to) control, [players’ fitness, skill training, replacing players, etc] and what change is due to things outside of your control, or put another way, is down to dumb luck [weather, referee mistakes, near-misses, etc].
In the Hot N Cold section above, beneath a topline of goal related totals, I have plotted how all the teams in the top five leagues in Europe performed relative to expected goals, offensively and defensively, as well as providing the final league position and the number of points earned at season end.
GS - xGS
On the left side we have the number of goals scored (GS) minus expected goals scored (xGS).
If this number is greater than zero, it means you’re scoring more goals than the quality of your team’s chances would indicate. Could be a great player making that difference he’s paid to make, it may also be a little luck, but in either case beware that dreaded regression to the mean!
If this number is lower than zero, you’re scoring fewer goals than the quality of your team’s chances would indicates. Could be your strikers are off the boil, could be a spate of bad luck, but in this case one tries to accelerate or at least not impede the regression to the mean.
GC - xGC
On the right side we have the number of goals conceded (GC) minus expected goals conceded (xGC).
If this number is greater than zero, it means you are conceding more goals than the quality of the other team’s chances would indicate. Might be that your defenders are somewhat asleep at the switch or simply that bad luck again, but again: accelerate or at least not impede the regression to the mean.
If this number is less than zero, it means your conceding fewer goals than the quality of the other team’s chances would indicate. Your defenders are stepping up a level or that wonderful good luck again but beware, always, that dreaded regression to the mean!
I have plotted them so the closer your bar gets to the middle, the “hotter” you are, i.e the more you are over-performing expected goals, whereas under-performing bars “cooler” are repelled towards the edges of the graph. Take a look through the past few seasons of the top five leagues in Europe and see how real-life performance compares to your priors.
Por ejemplo:
France 2016-2017
AS Monaco & PSG
Monaco thankfully interrupted what would have been eight seasons (as of COVID) of PSG dominance in the French Ligue 1 by smashing in the goals (a whopping 32.62 scored over expected, far and away the largest difference in this dataset) and getting just a little lucky in defense. What was ostensibly a 2-4-4 attacking formation certainly paid dividends this season, with Monaco way over-performing expected goals.
As for former champs and fellow rich kids PSG, they under-performed ever so slightly on both sides of the ball this season, they had just lost all-time-at-the-time top scorer Zlatan “I Am Football” Ibrahimovic to LA Galaxy, and though now-all-time top scorer Edinson Cavani did a fantastic job replicating Zlatan’s goal haul, bagging 35 to Ibra’s 38 in 2015-2016 season, no one else really stepped up replicate Cavani’s silver medal haul, the closest being Lucas Moura with 13 goals compared to Cavani’s 21 in 2015-2016.
Losing that many goals season over season was a major factor in their general under-performance, an under-performance that left them seven points adrift from this absolutely fire-emoji Monaco team in the end. After the dust settled, PSG learned from their mistakes and brought Monaco’s young starlet and now World Cup-Winning PSG star Kylian Mbappe (vid's better on mute), and some fella no one’s heard of named Neymar to bang in the goals. Monaco, shorn of not just Mbappe but most of that star squad, embraced returning to their role as a selling team (along with most every other team in every league, to be fair) and finished the most recent pandemic-shortened 2019-2020 season in ninth place.
Kylian Mbappe “Golden Boy” y “El Tigre” Falcao
England 2018-2019
Arsenal FC & Fulham FC
Two London teams, two season-endings with their own flavors of ignominy:
For Arsenal: no St. Totteringham Day as Tottenham finish just above them (again) in fourth, taking the last Champion’s league spot to boot.
For Fulham: relegation after just the one year in the Premier League after spending ~ $137 million dollars (recouping about $6 million) over the course that season
We can see above that Arsenal wildly over-performed on offense (9.65 scored over expected, highest in the league) and semi-wildly on defense (7.14 conceded below expected, good enough for top five), and all that to just miss out on a Champion’s League spot. This suggests improvements to the squad would be necessary to regain that former Fourth Place glory.
Fulham, meanwhile, had spent just over a hundreds million dollars on 20 new players, most of whom couldn’t manage to find any cohesiveness with each other or summon enough luck or skill on either side of the ball. I am happy to go out on a limb here and posit that this is irrefutable evidence that, no matter how hard you try, you cannot simply pay your way into successive seasons in the Premier League. It appears though, like Newcastle and Burnley before them, Fulham used the relegation parachute payment to good effect and keep short their stay in the wild west that is the Championship, so here’s hoping it’s less dire this round at Craven Cottage in 2020-2021.
A Fulham screamer from that season to balance it out (with max 0.1 xG it has to be said).
Spain 2017-2018
Real Betis & Getafe CF
In November 2017, Real Betis played Getafe to a 2-2 draw. Betis’ coach “El Maestro” Quique Setien described Jose “Pepe” Bordalas-managed Getafe’s play as “lamentable”, and “this is not football, this is something else.” This was somewhat less direct than Setien had been previously towards a Bordalas team, having called Bordalas’ 2013 Alcorcon team “painful to watch,” and lamented then that “[t]hey don’t let you play, just interrupt the game, waste time.” Bordalas, for his part, described his 2013 win with Alcorcon over Setien’s Lugo as “[t]he team who wanted it more won, the ones who went looking for the victory, and who showed a pair of b—s.” This, right here, is the (crude) crux of these two men’s distaste for each other’s brand of football and, supposedly, their dislike for each other in general.
Setien teams want to play beautiful, free-flowing soccer, long passing moves from which goals flow naturally. He’s a Cruyffian fundamentalist, a student of positive football and is fervently devoted to permanently having the ball. He also once told the Independent “[s]ometimes, how I feel about football, it doesn’t matter if a team wins or loses. What attracts me to a match is whether the teams play well, that there are footballers, that it goes beyond the result.”
Bordalas’ teams, by contrast, take the game by the … throat, and proceed to kill the action by fouling and wasting time. When the ball actually makes it into play, they soak up pressure comfortably in a coordinated low block and bide their time until they can maybe score on the break. For Bordalas, soccer games and goals, especially goals, are smash and grab affairs, things to be taken and not given and certainly not enjoyed by both sides. When it comes to Bordalas, if he’s a fundamentalist about anything, it’s that there is no ‘beyond the result.’
In this 2017 season, Setien had his high-flying Betis team playing his putting chances away left and right, but also conceding way more than their fair share. The Spanish Football Podcast started the hashtag #AlwaysWatchBetis this season after it became clear you could be assured of one thing during their games: there would be goals. Bordalas had just started his second season at Getafe having gotten them promoted from the second tier the season before (i.e his first season there).
Can you see styles of football in this kind of aggregate performance data? Almost certainly not, but in this case I do think you can see the imprints of each manager’s philosophy along with their attendant weaknesses.
Setien’s Betis did, in fact, play that beautiful flowing soccer, but while leading the league in goals over expected, they were also second worst in conceded under expected. This all suggests a porous, if maybe somewhat unlucky backline, but in the end, most of the fun of the #AlwaysWatchBetis era was knowing you’d get goals and more likely than not at both ends.
Bordalas’ Getafe, meanwhile, significantly over-performed in defense, managing to spare themselves a little over nine goals over the season. This made up for the fact that they somehow made the top ten as a newly promoted team while still having second lowest scored over expected in that cohort, i.e they got there without really scoring all that much. Yet for all their defensive solidity, they lacked incision up front, and incision was what they would eventually need to push them even higher up the table.
A coda on this twisting tale of two managers: Betis’ loss to Getafe in March 2019 was reportedly “one of final straws leading to Setien being fired by 'los verdiblancos'" that summer. Setien was briefly at the reins for FC Barcelona, a dream appointment for him considering his Cruyffian reverence, though it was sadly, in the end, a short-lived one. Barça ended the domestic season without winning La Liga for the first time since 2017 (not really his fault), and that before being knocked out of the Champion’s League 8-2 by Bayern Munich (at least a little bit his fault, him along with Alphonso Davies). As for Bordalas, his Getafe have only improved, even occupying a Champion’s League place for a non-trivial portion of the 2019-2020 season (pre-COVID, that is). Some of the claims to fame Getafe can boast of late: lowest possession per match in La Liga, fouls- and yellow cards-per-game, least amount of ball-in-play time, the highest percentage of goals from open play (82.4%), and, rather impressively if not surprisingly, no team needs fewer passes to create a goalscoring opportunity.
Further Viewing:
since La Liga, with their typical eye towards outreach, won’t let you embed videos with any of their “product” unless they’re from bein
A breakdown of a how Betis did, in fact, manage to break down Getafe for a Sergio Leon match-winner.
To say Getafe play in an obstructive manner is not to say they aren’t capable of converting some low-xG thunderbolts, note in particular the sucker punch Gaku volley against Barça.
Spain 2019-2020
FC Barcelona & CD Leganes
(full disclosure: have been a fairly avid Barcelona fan for a little over fifteen years now,
but for reasons which will become clear on reading, positive bias will not be an issue here)
FC Barcelona embarassed themselves in the 2019-2020 season, and it has less to do with their eventual league position than you think. Barcelona as mentioned above, failed to win La Liga this season, while still over-performing expected goals on both sides of the ball.. They had a league leading 7.47 scored over expected, (as an aside: maybe COVID has indeed had a dampening effect on that overall goals scored, an effect which flows downstream to this somewhat insipid maximum, but that's an area of analysis for a more nuanced dash to come), and a better than average defense with an exceptional goalie who kept their heads above water with the conceded just under expected and despite losing out on the league managed to canter to second place twelve points ahead of a offensively-woeful Atletico Madrid side at third.
Leganes played their final game of the season against already crowned champions Real Madrid with their fate only somewhat in their hands - they needed to better Celta Vigo’s result at bottom-feeders Espanyol. As it turned out, despite holding the champs to a 2-2 draw at home (actually an empty stadium in the part of Spain hardest hit by COVID), Leganes were relegated after Celta maintained a scoreless draw at already-relegated Espanyol. It would have been one thing if it was just their defense, after all they conceded the most goals over expected (5.42) out of all teams in Spain, but the way Leganes’ offense suffered (third worst in Spain at 10.1 goals under expected) has some extrinsic influences that need to be unpacked.
Some solid final third play from Martin Braithwaite during his time at Lega (vid {and accompanying sweet track} courtesy of the sanctified bein on youtube)
In the January transfer window, Leganes, second bottom at the time, lost their second highest scorer Youssef En-Nesyri (four goals for Lega, a respectable 0.26 goals per 90 for the whole season) to Sevilla, fourth top at the time, who paid his $24 million buy-out clause and thus vacuumed him up the table. Then, in February, after the transfer window had supposedly closed, FC Barcelona, reigning and current (at the time) champions of La Liga, lost Ousmane Dembele to injury. With Luis Suarez already out and having sold two(!) strikers in the January window while recouping exactly zero strikers (despite that being apparently of paramount concern), Barcelona engaged in the most fair-minded and logical recruiting decisions they could fathom: the champs, (who literally already have a B team playing in the lower leagues it would seem for this very contingency), had to emergency trigger the buy-out clause of Martin Braithwaite, highest scorer at Leganes (6 goals for Lega, also 0.26 goals per 90 for the whole season), who were still second bottom. What was Leganes’ recourse, you ask? Well, they had none.
In Spain, in case of injury related squad emergency, a team can buy (read: snatch) a replacement player with one big caveat: this transaction is not officially recognized by UEFA, FIFA’s European administrative arm, (themselves no saints historically either, but I digress), and therefore you can only “buy” players within Spanish leagues and those players cannot play for their new team in European competition. Having now lost their top goal producer, Leganes were, according to the “rules,” not given permission to sign a replacement, and were thus left to hope Oscar Rodriguez could will them out of the relegation zone (which, to be fair, producing 0.42 goals per 90, he almost did). The difference Martin Braithwaite made at Barcelona was marginal at best when you consider the quality of players for whom he was standing in, Dembele and Suarez provide far more goals and assists per 90, and all this is not even factoring in the G.O.A.T. The difference Braithwaite was making and could have continued to make at Leganes, considering his contribution for Barcelona in La Liga, could very well have been consequential for Leganes.
I do not want this to sound, at all, as if I am somehow chiding Martin Braithwaite. He got an opportunity to take a big step up in his career and for my money, he ‘stuck it in the top corner'. I would, in fact, go as far as saying that he was one of Barcelona’s best players on the day in his substitute appearance for Barcelona against perennial Clasico rivals and eventual champions Real Madrid. He even managed to get off a shot on target. Therein lies the counterfactual tragedy, though: if he was as good as he looked for Barcelona for 20 minutes against Real Madrid, could he maybe, possibly have scored a third goal for Leganes against Real Madrid on the final day of the season thereby keeping them up and sending Celta (deservedly) down the river? Still, in all, good luck to him in the prem next year.
What really grinds my gears about what Barcelona did is how negative sum it was, not just in how it appeared at the time but in how it turned out in the end. No one will take La Liga seriously if all the teams underneath the top three lack legitimacy, and legitimacy is hard to build when you have a bloated hegemony parasitically siphoning talent from little guys fighting relegation. Barcelona’s board (decadent and gross) were so desperate to win they had no problem kneecapping the guy who was already limping, and in the end the worst part is that it’s probably more that he actually saved a lucky Barcelona from sliding further down the table.