Borussia Dortmund face Bayern Munich in Germany's biggest club game on Saturday, but the build-up has been overshadowed by the brewing transfer saga involving Marco Reus, who looks destined to move on next summer.
The contractual clause which allows Reus to leave Borussia Dortmund is activated in 2015 and Bayern remain at the front of the queue of Europe's elite for the forward.
It is scant surprise that it was Bayern who instigated the most recent spat between the two clubs. Bayern CEO Karl-Heinz Rummenigge let the cat out of the bag in August by confirming the buy-out clause in the player's contract.
"We know that he has a lot of quality," he told Sport Bild. "And we know his clause. For us a young German national player of such quality is interesting. But I do not want to make unrest in Dortmund."
Bayern's discussions of Reus have caused outrage in Dortmund with the club forced to issue a statement warning the German record champions off any more talk concerning their forward. Nonetheless, after spiriting Gotze and Robert Lewandowski away from the Westfalenstadion in consecutive summers, Bayern will be back for a third Dortmund star this year.
"If a German international has an exit clause and his contract is running out, Bayern is obliged to think about him," Rummenigge told Sport 1. "With Marco Reus, his release clause is known."
But Bayern are not the only club in the picture. Here is a player, in his prime, with a tantalisingly low fee attached - only €25 million from next summer.
Now Manchester City also intend to join the fight for his signature. It means that Reus, one of the continent's finest players, will be at the centre of a monumental transfer tussle with any number of outcomes still possible.
City have a long-standing interest in Reus and tried to sign him once before, only to be rebuffed. Txiki Begiristain, City's director of football, has admired the player since his Borussia Monchengladbach days and is hopeful of teaming him up with Sergio Aguero in a dream attack at the Etihad Stadium.
The Atletico Madrid president, Enrique Cerezo, also claimed over the summer that Reus had turned down an approach from Manchester United.
Liverpool have been strongly linked too with the attacker and could reasonably be expected to submit a bid once the contract clause kicks in.
There were also rumours over the summer that Real Madrid were monitoring his situation.
That Reus, at 25 and with an established Champions League club, has a release clause in his contract in the first place is a curious development. But Dortmund CEO Hans-Joachim Watzke admitted that inserting one was the only way to beat rivals to Reus in 2012 when he left Gladbach.
And just as Gladbach lost Reus for relative pittance against their wishes, Dortmund more than likely will too despite their attempts to tie him to a new deal.
This has not been a good year for the forward and if he was ever going to be tempted to leave, now would be the time. Dortmund were second best to Bayern in the Bundesliga as well as the DFB-Pokal last season and look no better this time around.
While his Germany team-mates were celebrating the World Cup win in Brazil, Reus, who should have been a key part of the team, was half the world away watching on television with a damaged ankle. Reus tore ligaments in the final pre-tournament friendly against Armenia and missed the tournament altogether.
He repeated the injury in the Euro 2016 qualification defeat of Scotland and is only now, in late October, coming into the Dortmund team on a regular, consistent basis.
And how they need him. Klopp has been without key players all season, Reus, Mats Hummels and Ilkay Gundogan chief among them, and are now languishing in 15th place in the Bundesliga after nine matches. Their business model is only truly sustainable if they maintain Champions League football. Dortmund have got to improve, drastically, in the league to have any chance of making the top four this season. Otherwise they will again have to cut their cloth accordingly.
The club earned €34,725,000 [£27.3m] from Champions League participation last season and that shortfall will have to be met in player sales. Reus's departure may seem inevitable but they could also be forced to cash in on the likes of their captain Hummels.
“For Dortmund it is getting harder and harder to keep Marco," Dortmund legend Jurgen Kohler told Bild recently. "The club can only keep hold of Reus if they invest properly for the next four or five years. Bayern will not let up in their spending. At the end of the day, I’m sure it is a question of money."
Their recent poor league form, which now stretches to six games without a win and just one point from a possible 18, has meant that contract renegotiations with Reus have been delayed. The club had hoped to improve Reus's wages as well as remove the release fee - scheduled to drop next summer. His current deal runs until 2017 but there will be no contract discussions until the poor run is over.
Reus, however, is a hometown boy and the hope, still, at the club is to provide him with the perfect conditions to thrive.
"Marco [Reus] feels very comfortable at Dortmund and we feel comfortable with him," Watzke told Sport Bild. "He has an even closer relationship with the club and the city than Mario Gotze did and I expect him to stay.
"Marco was born here, his family live here and his whole life has always been based here. He knows that BVB is the perfect place for him. I am sure of that."
Watzke also warned Reus against the potential pitfalls of life away from Dortmund. Nuri Sahin and Shinji Kagawa left the club for Real Madrid and Manchester United respectively only to find that the grass was not greener on the other side.
"I know Marco, I think quite well, and I can say that things with him are not primarily about money. We will hold talks with Marco, in which it will be important to show our total package," Watzke told WAZ.
"It consists of the economy, ambitions and extreme confidence that we give to the player. I have a feeling that our players are happy with us. For those who have moved, I had the impression it was not always compelling. To put it mildly.
"Marco Reus as a player from Borussia Dortmund can characterise an era, as a legend. This is, for my taste, much more important than two titles more on the CV."
But Reus' underwhelming year to date might have him considering his options. He will not win the title with Dortmund this year, that's for sure, and the club's big hope is to win the Champions League. They are going strong in that competition but are by no means a sure bet to win it outright.
Therefore, after missing out on the World Cup, Reus may no longer be prepared to play the waiting game and instead move to a club that is primed for immediate success, like Bayern or City.
In the recent past, Eden Hazard, Gareth Bale and Luis Suarez have all been at the centre of drawn out transfer sagas. Now it is Reus's name which will dominate the transfer landscape until next summer.