Mason Greenwood, Finishing Shenanigans, and the Importance of Creating Realistic Expectations for 18 Year Olds

Image: Wikimedia Commons

By: Kees van Hemmen

It’s pretty safe to say that Mason Greenwood has gotten off to a hot start with Manchester United. With 12 goals and 4 assists in just over 1600 competitive senior minutes, the 18 year old has drawn praise from far and wide for his maturity and goal scoring prowess. Man United legends like Gary Neville and Andy Cole have expressed how impressed they are with him, and recently departed striker Romelu Lukaku has tipped him as the most promising youngster with the club, saying, “Greenwood that boy coldddddd.” Marcus Rashford, too, has praised the young striker’s “frightening talent.”

One particular skill that Greenwood has been tipped for is his immaculate finishing ability. This bears out in the numbers, too, as Greenwood has managed 10 goals from 4.5 NPxG across league and European competition. Man United manager Ole Gunnar Solskjaer, quite the accomplished finisher himself, has also appraised the 18 year old's finishing skills. When asked which of Anthony Martial and Marcus Rashford was the more natural finisher, the gaffer said, “Natural finisher? Well, they've still got a way to go, because Mason's more of a natural finisher than those two.”

This raises some questions, however, as xG over performance is always saddled with an accompanying concern: how sustainable is this? Plenty of strikers have had lauded club campaigns while over performing xG, only to come crashing back to earth the ensuing season. This is rarely the narrative, though, as many posit instead that the striker in question is simply “past it” or a one season wonder, when the reality is what they were doing in the first place wasn’t replicable. With this in mind, I will attempt to investigate just how sustainable Mason’s production has been this campaign, and what can be expected of him going forward.



In the visualization above, we see xG mapped against finishing over performance. In red is Mason Greenwood, and we can immediately see just how well he’s finishing. Only one forward in Europe’s premier competitions is exceeding his xG on a per shot basis at a higher rate: former RB Salzburg and current Borussia Dortmund man Erling Braut Håland. Håland’s own finishing might warrant an article of its own except, he’s averaging 0.8 NPxG per 90 as it is. For the Norwegian, it doesn’t really matter if he can’t finish at this rate going forward, because he’s still putting up elite shot quality and volume. For Mason, however, it does. His NPxG values (just over 0.30 NPxG/90) aren't high enough for him to maintain strong goalscoring output without extreme finishing over performance. Luckily for him, that's exactly what he's doing.

We've now seen just how well he’s finishing, but it still doesn’t tell us how sustainable it is. For answers to that question, we have to look further back, to a greater sample size.





The two plots above have an identical x axis to the first graph showing Greenwood’s finishing. Essentially, they show how finishing ability becomes less and less pronounced as you increase the sample of shots taken. Notice how the cluster of players on the axis gets closer to 0, and outliers get less pronounced, as the sample size increases from 1 year to 3 years and then 3 years to 6 years. What does this mean for Mason? As time goes on, Greenwood’s level of finishing is increasingly unlikely to continue. Greenwood’s 17% xG over performance per shot (effectively the xG he has ‘added’ to each shot he’s taken this year) is more than 12% higher than the next nearest finisher over a 6 year sample. Essentially, he can’t maintain anything like this. Even if he is in fact an elite finisher – as the early signs do indicate – the odds that he, at 18 years old, is already by far the greatest finisher in the modern game are basically zero. That, on its own, isn’t enough though. It’s easy to say he’s not as good as his finishing suggests, it’s something else entirely to say what we can realistically expect going forward. Let’s take a look.

One of the most successful and replicable ways to exceed xG for any player is to be equally competent shooting on both feet. This is because it fools most expected goals models, which attribute lower scoring probability to shots taken with the weaker foot [EDIT: most expected goal models do not factor in footedness, however, the following point on the ability to get shots off still stands independent of this inaccurate assertion]. This doesn’t negate the value of the skill, however. Players who aren’t capable of shooting reliably with their weak foot often opt instead to force shots with their strong foot, resulting in lower quality chances and blocked shots. Players who can shoot with their weaker foot aren’t “fooling” the model, they’re actually producing shots others cannot. A great example of this is Tottenham forward Son Heung-Min, who has over performed his xG by nearly 18 goals over the last 6 league campaigns on the strength of his two footedness. This is pertinent because, as Greenwood has come through United’s youth system, there’s been a lot of talk of his status as “a true two-footed finisher.”

[A note on this shot map: the data was manually collected by yours truly using broadcast footage, so the data quality is probably somewhat dicey. It’s also worth noting that a disproportionate number of these shots are goals, because they, for obvious reasons, are easier to find video footage for. All the same, I use it largely for stylistic analysis, so the consequences of the data quality pitfalls are less pronounced.]

Looking at this shot map, that doesn’t appear to be the case. This plot shows Greenwood as clearly left foot dominant, despite a) his preference for taking penalties with his right foot (which is perhaps more a statement than he can do it than anything else, as the two penalties he’s taken for the senior side with his right have been fairly tame strikes) and b) the narrative being that he’s ‘truly two-footed.’ While Greenwood is certainly more comfortable on his right foot than most left-footed players, he shows a clear preference for his left foot. In this sample, 9 of 30 shots have been taken with his right foot. In League and European competition this term he has taken 16 shots with his left as opposed to 7 with his right, and made 347 passes with his left versus 106 with his right. This actually still places him in the 85th percentile for two footedness in passing, but it doesn't change the fact that he has an overwhelmingly dominant foot. Not only that, but he has only scored one goal with his right foot. Though he is perhaps a willing and capable shooter with his weak foot, this clearly isn’t the root of his finishing over performance.

If Greenwood isn’t following Son’s model of xG over performance, then he must just be lucky, no? Not exactly. There is another archetype of xG over performer that Greenwood fits in with more comfortably.



Players like Arjen Robben, Paolo Dybala, and Lionel Messi have all consistently exceeded their expected goals through another avenue: precision finishing from the edges of the 18 yard box, specifically the right half space. One player’s shot map in particular evokes Greenwood’s, albeit in significantly greater volume:

[this visualization was burglarized from another article on finishing and goalscoring trends by James Yorke of StatsBomb]

Mo Salah, in the 2017-18 season, recorded one of the greatest finishing campaigns on record by xG over performance per shot. He did it by cutting onto his left foot and finishing deftly into the bottom corners of the net, over, and over, and over again. Incidentally, this is where Greenwood thrives as well. Their hot spots aren’t exactly identical – Greenwood shoots and scores from slightly more withdrawn and right sided positions – but their profiles are similar: left-footed players capable of razor-like precision from a very specific part of the pitch. Salah is obviously the far better player at this point, and there are important stylistic differences (Greenwood overwhelmingly plays in front of the defense, whereas Salah gets in behind more), but the comparison still holds. In the piece this visualization came from, author James Yorke even remarks on the success defenses have had forcing Salah onto his weaker right foot and into tighter shooting angles. The same trend can be seen in Greenwood’s shot map, though perhaps his ability with the right will prove superior to Salah’s given the narrative around his two-footedness at the youth level. Different goalscorers of this profile (left footers who thrive in the half spaces) have learned to deal with being shepherded onto their right differently: Messi by bearing down on the keeper and chipping into the far corner, Robben by using change of pace and excessive faked shots to allow him to stay on his left. How Greenwood chooses to do this will have a great bearing on his ability to continue outpacing xG as well.

Though we must be careful with the small sample size Mason has provided, the finishes he’s made for most of his goals have in fact been excellent. 5 of the goals have been almost perfectly slotted into the bottom right corner, along with a powerful strike into the top left, a tight angled shot that kissed both posts, a slightly deflected bar down effort against Newcastle, and a perfectly measured finish between four defenders in the ICC against Internazionale (that, yes, may have had an element of luck). Of his other two successful finishes, one was a first time sliding half volley – not easy in its own right, but not necessarily replicable either – and the other a clever near post effort against Partizan Belgrade. The second of these two is worth a closer look.



What Greenwood does here may shed some light on his finishing performance. Not only is he composed, but he cleverly shapes his body as if he intends to finish to the far post. This sends the goalkeeper the wrong way, which ultimately creates what equates to an open net finish at the near post. This isn’t the only example of Greenwood doing this. There are elements of the same deception in his goals against Everton in the league and Rochdale in the League Cup. Though he doesn’t send the keeper to the floor in those instances, he still shapes up to go far post and then slides the ball hard towards the near post. It catches the keeper off-balance, and may have a small bearing on his finishing over performance.

All of this said, Mason’s current finishing pace cannot be expected to continue. No player on record has maintained his current finishing rate over multiple seasons. To expect Mason to do so would not only be unwise, but unfair to him as a prospect. It’s far more likely that the young United forward will regress to the mean as a finisher, though early signs indicate that he can perhaps slot into the top tier of finishers, those who add between 3 and 5 percent goal probability to each shot they take.

Perhaps you are now wondering if United should be worried about Greenwood. After all, if half of his goal scoring production appears unsustainable, wouldn’t that leave him with relatively pedestrian numbers?



Well, yes and no. If you compare Mason to other forwards across Europe’s top competitions this campaign, things don’t look great. He’s around the fiftieth percentile in NPxG per 90, touches in the penalty area, shot assists per 90, dribble success rate, crosses per 90, and final third pressures per 90. That’s… most of the primary functions of a modern forward that he’s decidedly average (or ‘median’, if you’re a statistical pedant) in performing. Even worse, he’s not prolific or particularly effective in the air, the shots he assists are of extremely low quality, and so are the shots he himself takes. These don’t read as the numbers of an elite young forward.

A closer look, however, tells a different story. Greenwood is still in the 77th percentile for shots per 90, and he sits in the 92nd percentile for turnovers. A prolific shooter who doesn’t give the ball away is still a useful profile. Given that he’s in the sixtieth percentile for offsides per 90, it appears he’s also playing a healthy amount of the game on the shoulder, which may indicate his shot quality will have the opportunity to increase in the future. And this is when compared to forwards of all ages. If we look at Mason compared to U20 forwards in the same competitions over the last 3 years, we are again confronted with an entirely different narrative.


Here, Greenwood profiles in the 84th percentile for shots per 90, the 80th for touches in the final third, the 73rd for NPxG per 90, and a whopping 98th percentile for turnovers per 90. For reference, Juventus star forward Paolo Dybala (whom Greenwood was compared to earlier in this piece) sits in the 75th percentile for NPxG per 90 amongst all forwards. That’s a pretty good track to be on in terms of development, especially when you consider that most of Mason’s contemporaries are still playing for youth sides. The bottom line remains that, at 18 years old, he’s producing elite level xG sums for his age group in a high usage role, while hardly conceding possession (something young forwards are prone to doing, and often spend much of their early playing years learning to cut out). Not to mention he’s finishing at an elite level, which, for all of the red flags it can – and has – raised, is actually a good thing. Sometimes it’s easy to forget that when we talk about expected goals, it’s not the actual over performance that’s a problem, it’s what the over performance tells us about what may happen in the future.

Essentially, it’s pretty safe to say that if he continues along the same development trajectory, there’s no need to be worried about Mason Greenwood. That’s not the same as saying that he’ll keep more than doubling his xG tally, though. There is likely some sort of finishing slump, or at least a finishing cool off, on the horizon for Mason. When it comes, be kind. There’s still a lot to be excited about.

Data Sources:
https://understat.com/league/EPL
https://fbref.com/
https://fbref.com/en/players/58eee997/Mason-Greenwood
https://statsbomb.com/2019/03/evaluating-mohamed-salah/