After a storming start to the 2017/18 season, things quickly went pear-shaped for Borussia Dortmund.
Under former Ajax manager Peter Bosz, endured a run of just one win in more than two months – and even that was against third-tier opposition in the DFB Pokal, slipping from the top of the Bundesliga to fifth.
Back-to-back victories under new boss Peter Stöger steadied the ship going into the winter break, taking the Black and Yellows up to third. But BVB's uptick in form has done little to quell rumours of a January exit for star striker Pierre-Emerick Aubameyang, who has been consistently linked with a Premier League move for more than two years now.
And having failed to secure his move away so far, Aubameyang appears to be doing his best to burn his bridges at Dortmund. He was left out of the matchday squad for Sunday's goalless draw against Wolfsburg after an incident relating to a team meeting with English youngster Jadon Sancho making his first start in his place.
Speaking about the incident, Stöger said: “It was a relatively important session that he stayed away from, which showed me that he is not so focused.
“He was surprised, he did not quite notice it for himself. But for us it was a clear case.
“The session was clearly announced in WhatsApp groups that are today on tablets. If he is not there, someone else is playing, who is totally focused.”
Who is Pierre-Emerick Aubameyang?
Dortmund signed Aubameyang from Saint-Étienne in the summer of 2013. The France-born Gabonese international had impressed with Les Verts, finally finding a home after years of being loaned out by AC Milan.
Before moving to Signal Iduna Park, Aubameyang had played most of his football on the right wing. But when Robert Lewandowski joined rivals Bayern Munich in 2014, then-BVB manager Jürgen Klopp converted the lightning-fast wide-man into a centre-forward.
In his first term as a striker, Aubameyang helped Dortmund overcome the loss of their Polish hitman with 25 goals in all competitions. As he grew more accustomed to his new role and further developed his finishing skills he became even more prolific, returning 39 goals in 49 outings in 2015/16, and 40 in 46 last season.
Linked with Manchester City two summers ago and open about his desire to someday represent Real Madrid, proposed big-money moves away from the Black and Yellows have not yet materialised for Aubameyang, but he might now be ready to force through an exit.
What are Aubameyang's main strengths?
Aubameyang's main asset is, without question, his pace. Easily the fastest elite-level striker on the planet, no defender can hope to catch the Gabonese once he is in full flight.
He is also a ruthless finisher, remarkable considering he isn't a natural striker and only found a regular home in the position in his mid-20s.
Aside from his outstanding goal-getting ability, Aubamayang is also a capable creator when his old winger's instincts kick back in.
It's a part of his game that has been de-emphasised over the last 18 months as he has developed into more of a penalty-box poacher, but the former Milan man is exceptional when breaking down the inside-right channel, capable of excellent low crosses into the area.
As we see in the above image, taken from last season's Champions League clash between Dortmund and Real Madrid at the Santiago Bernabéu, Aubameyang's searing pace allows him to beat Sergio Ramos to the ball and sprint clear of the Spanish defender down the right.
Then, as he approaches the penalty area, Aubameyang exhibits perfect timing and execution to swing a low ball into the path of Marco Reus, who dutifully dispatches the clear-cut chance the No.17 has forged.
What are Aubameyang's main weaknesses?
Although he is able to lead the line as a lone striker, Aubameyang is only effective in such a role if supported adequately.
During Dortmund's downturn in form, the 28-year-old looked isolated at the point of attack in Bosz's 4-3-3 system, which didn't allow for the same degree of fluidity espoused by predecessor Thomas Tuchel.
Aubameyang's best form came with either Henrikh Mkhitaryan or Ousmane Dembélé moving inside from the flanks to create in behind him in the No.10 zone with Reus, when fit, pushing up alongside him from the left side.
He can offer an outlet in the channels, but Aubameyang is no target man and is not able to effectively hold the ball up and link play when there is too much space between him and his attacking colleagues.
Aubameyang has also had some disciplinary issues, suspended internally for an unauthorised trio to Milan last season and again for turning up late to training this term.
How much is Aubameyang worth?
When linked with Manchester City in the summer of 2016, there was talk of Dortmund demanding as much as £70million for their star striker, while figures of £50-60million were mooted in transfer speculation surrounding the former Monaco loanee before this season.
However, Aubameyang turns 29 in June. As a player whose main asset, one that his game is built around, is pace, many prospective buyers may feel that he doesn't have a great deal of shelf life at the highest level.
As such, if they are to sell either in January or next summer, Dortmund might reasonably expect to receive a fee somewhere in the £40-50million range. Aubameyang is undoubtedly an elite-level striker, and the transfer market is inflated at present, but the player's age will count against him.
Why Arsenal should sign Aubameyang
According to Alexis Sánchez when he departs the Emirates this month.
Despite spending much of his early career as a winger, Aubameyang made the switch to centre-forward when Lewandowski left Dortmund to join Bayern Munich in 2014. Since then, the 28-year-old has carefully honed his playing style to focus on finding space and taking chances in and around the penalty area.
As such, he would not be a direct replacement for Sánchez in the Arsenal line-up, as the Chilean plays predominantly from the left side of Arsenal's attack, and Aubameyang is unlikely to consider reverting to a wide role having established himself as a striker of the highest order.
This would mean he would be coming in to compete with record signing Alexandre Lacazette for a starting berth. Or perhaps Arsène Wenger has a change of formation in mind and will look to pair the Dortmund star with the Frenchman.
While Lacazette's presence means Arsenal are in no grave need of a new No.9, Aubameyang, with his pace and precision finishing, could add a new element to the Gunners' attack.