Another COVID-donation request fulfilled this week. Hope you’re all staying safe and well. Zach asked for a piece on Pierre-Emerick Aubameyang and aging strikers. Here is that piece.

It’s been a rough week for Pierre-Emerick Aubameyang. First, the Arsenal captain was benched for showing up late to a meeting before the team’s biggest game of the Premier League season, the North London Derby. The Gunners won -- and looked great without him. Midweek, he went the full 90 against Olimpiacos in the Europa League, but missed a full expected goal’s worth of chances. Then, on Sunday, back in the lineup in the Premier League against West Ham, Aubameyang went the other way: didn’t take a single shot or create a single chance before being subbed off with 10 minutes to go and his team still in need of a goal.

The past week serves as a tidy little representation of Auba’s 2020-21 season, too: not enough shots, and even fewer goals. In 21 Premier League starts this campaign, the 31 year old has scored seven non-penalty goals on 7.4 non-penalty expected goals, per FBref. Toss in the one assist, and he’s averaging just 0.37 non-penalty goals+assists per 90 minutes in the league. Among qualified players,¹ that’s the 49th-most-prolific rate in the league -- behind the likes of Arsenal cast-off Danny Welbeck, David McGoldrick, who almost single handedly broke every xG model with his seemingly blindfolded finishing last season, and current Arsenal flop Willian.

Amidst their captain’s struggles, though, Arsenal might finally be heading in the right direction. After a 2020 filled with awful performances that were somewhat masked by an FA Cup victory and a couple flukey wins over Liverpool and Manchester City, Mikel Arteta’s team is starting to look vaguely like what a successful soccer team looks like in 2021. Since January 1, they’ve attempted the fifth-most shots and conceded the sixth-fewest. More importantly, they’re routinely out-shooting their opponents, which rarely happened over Arteta’s first year in charge. They’re completing the sixth-most passes into the penalty area, and they’re completing 56.2 percent of the final-third passes in their matches -- fifth best in the league. And they’re winning the ball higher up the field than all but five other teams. Take all those characteristics, toss ‘em together, and it adds up to the fourth-best non-penalty expected goal differential in the Premier League since January 1. You can’t just ignore what happened from September through December -- this same group of players produced those uninspiring results -- but at the very least it seems clear that Arsenal are back among the same group their revenues suggest they should be in: one of the six best teams in the Premier League.

What’s more: they're doing it with one of the greener teams in the league. Per FBref, Arsenal’s playing-time adjusted average age is 26.7 -- tied for fifth-youngest in the league. Bukayo Saka has played the most minutes of any outfield player, and he’s just 19, while 23-year-old Kieran Tierney comes in third in that same list. Plus, you can pretty closely track the club’s improvement with the arrival of Real Madrid loanee Martin Odegaard (22) and the increased playing time for 20-year-old Emile Smith-Rowe.

Given all of that, there are two ways to look at the Aubameyang situation: 1) If this is just a down year, Arsenal will soon have a world-class striker to place on top of a steadily improving team that’s finally creating the volume of chances worthy of said world-class striker. Or 2) Arsenal made Aubameyang one of the highest-paid players in England right as he’d begun to decline, and it’s not gonna get better from here. Unfortunately, history suggests that no. 2 is probably closer to the truth.

Over the summer, fresh off an FA Cup victory, Arsenal gave their 31-year-old club captain a three-year contract that, at the time, made him one of the five highest paid players in the Premier League, according to the site Spotrac. Auba had played two-and-half seasons in the Premier League; he’d scored an average of 19 non-penalty goals in his two full seasons and hit nine in his initial half season. With penalties and assists added in, he was contributing to more  than 20 goals per year. Based purely on past performance in the Premier League, Aubameyang seemed to all but guarantee elite goal-scoring, which is the most valuable skill in a low-scoring sport like this. Hence: the contract.

Of course, players don’t perform in a vacuum, and like all of us, they have to deal with the constant, frustrating constraints and degradations of the human body. When they’re younger, they have to train it to consistently do things that it’s never done before, over and over and over again. Then, they have to figure out how to do those things without getting hurt. And before you know it, the body starts fighting back, begins forgetting forever how to move as fast, as easily, as often. As Leeds manager Marcelo Bielsa once put it: “If players weren’t human, I’d never lose.”

According to analysis by Michael Caley, the performance peak of a professional soccer player comes quick and disappears even quicker. He found that most players peak between the ages of 25 and 28, with some positions lasting a little longer in the limelight:

Wingers tend to peak and decline the earliest. Wide attackers under the age of 23 play more minutes than U-23 players at other positions, but wide attackers over 30 are much rarer than strikers or center-backs of an equally advanced age. While most of the curves are well on the downslope by 30, the curve for center-backs by contrast doesn't really begin to decline until 31 or 32.

This suggests a general rule. Players tend to get slower and generally lose athleticism as they age, but they also gain skills and know-how to balance that out. Positions that require the most athleticism are a young person's game, whereas older players will more often be found at positions that most prize guile.

Caley even puts the positions on a spectrum of volatility, i.e. which ones are most affected by age, in order? It goes, starting with the most age-affected: “Wide attacking midfielder, central attacking midfielder, full-back, central midfielder, striker, center-back, goalkeeper”.

Aubameyang is a winger-turned-striker-turned-winger-slash-striker. He started off on the wing, as players with his pace often do, but he really exploded when Thomas Tuchel took over at Borussia Dortmund and started to play him through the middle. However, that period also coincided with what would be considered Aubameyang’s peak -- his age 26 and 27 seasons.² In those two years under Tuchel, he scored 51 non-penalty goals in the Bundesliga. He never took a ton of shots, but his speed and penalty-area savvy allowed him to get on the end a collection of absurdly high-quality chances. The average shot in a top European league has an xG value of about 0.11 -- or an 11 percent chance of being turned into a goal. In his two years under Klopp, Aubameyang averaged around 0.15 xG/shot. Under Tuchel, that number leapt up to 0.25. He also added about an extra shot per 90 minutes to what he was doing under Klopp, which resulted in those 51 goals. The chances in this image are sized by the xG value of the shot:

In his first half-season with Arsenal, Aubameyang maintained the incredible shot quality but lost that extra shot he’d gained under Tuchel. The results were still fantastic; he didn’t play enough minutes to qualify for the FBref leaderboards, but he would’ve been seventh in the league in non-penalty goals per 90 minutes and second in goals+assists per 90. In his first full year, he scored the fourth-most non-penalty goals in the Premier League (18), and then last year increased his total (20) and his place on the leaderboard (second).

Except, something changed last season. He spent some more time on the wing, but that’s not the notable thing. No, for nearly his entire career, and like most players in the world, Aubameyang finished his chances at an average rate. Before last season, in the Bundesliga and the Premier League, he scored 115 non-penalty goals on 116.32 xG. Last year, though, those 20 goals came on just 13.17 xG. Only the year before, he scored fewer goals (18) on more xG (19.16) xG. In fact, his shot quality dropped back down to those pre-Tuchel levels last season, and there was also a slight decrease in shots. Had he suddenly become Leo Messi whenever he kicked a ball? Or did some finishing variance mask an oncoming decline?

If you ignored the outcomes and just focused on the process, Aubameyang’s shot production could serve as a dictionary definition for “career arc”, and the development tracks pretty tightly with what Caley’s research found:

This season, the finishing has reverted back to where it’s always been, and he’s lost about an extra shot from every other match while maintaining that lower level of shot quality. The result: 0.33 goals per 90 and 0.31 xG per 90.

Now, since the turn of the calendar, he’s been better -- back above 0.20 xG/shot and more shots, resulting in 0.56 xG per 90 and 0.66 goals. That’s down from his peak, but way more in line with his career average, and if he can keep that up for a full season, then Arsenal will be in much better shape. At his peak, Aubameyang was the most efficient superstar of his era, all well-times bursts into the six-yard box and seamless stutter to open up space at the far post. All of a sudden the ball’s in the back of the net — and wait, when did Spiderman get here? That’s not coming back, but some abbreviated form of it would change the calculus for his club over the next couple years.

Except, for an individual player, that recent uptick comes from a small sample of games. It also seems like a really specific story to explain away why this one, specific player will buck the larger historical trend that it seems like he’s being swept along by. Just look at the chart again; age-related improvement and decline doesn’t get any clearer than that. Plus, part of what makes a peak season is the player’s ability to produce week in and week out -- not just play well for a couple months.

Pure production wasn’t Arsenal’s only consideration when re-upping Aubameyang. It must’ve made a lot of fans happy, and there’s surely some benefit in showing players that you’ll reward them for playing well, rather than purely paying for future projections. You can’t run a soccer club purely by optimizing inputs and outputs. Players are, after all, human. However, building the best soccer team possible should theoretically be one of Arsenal’s main goals, if not the main goal. And while that team as a whole really does seem to finally be getting better, they’re left with a potentially awkward situation: their highest-profile player is headed in the other direction.