Marco Rose will swap Borussias in the summer, leaving Mönchengladbach to succeed Lucien Favre as the long-term coach at Dortmund. How will Die Schwarzgelben line up once he gets there?
Leipzig-born Rose came to prominence as a coach at Red Bull Salzburg, whom he guided to back-to-back Austrian Bundesliga titles, the second of which was part of a domestic double in 2018/19.
Dortmund goal-machine Erling Haaland was part of his Salzburg ensemble then, but perhaps the biggest clues about Rose's BVB can be found an hour's drive west of the Signal Iduna Park, where the inbound coach has moulded Gladbach into a Bundesliga force…
The 44-year-old steered the Foals to a fourth-place finish in his first season, Gladbach joining Bayern Munich, Dortmund and RB Leipzig in this year's UEFA Champions League, where they have taken points off Real Madrid and Inter Milan on their way to the last 16.
Gladbach, like Dortmund, have invariably lined up in a 4-2-3-1 system this season, using the formation in all but five of their Bundesliga fixtures in 2020/21 - one of which was a 4-2 win over BVB in January. They started with a nominal 3-4-3 that day, but key characteristics have been prevalent throughout the campaign.
Lars Stindl captains the team from the No.10 position, and has top-scored with 13 goals and 12 assists in all competitions; while the set-up is underpinned by a centre-back pairing of Matthias Ginter and Nico Elvedi, the former a first-choice for Germany, the latter the owner of the league's highest pass completion at 93.6 percent.
Watch: Rose's Gladbach under the tactical microscope
Christoph Kramer, or sometimes Denis Zakaria, alongside Florian Neuhaus, provide a unique double pivot, meanwhile. Kramer brings the grit to Neuhaus's grace, which means Gladbach don't necessarily have to change their shape depending on whether or not they have possession.
Apart from Gladbach's 4-2 win at the start of the year, there has been precious little to separate the two Borussias this season, with Dortmund actually four places and six points better off than Rose's current employers, whom they'll meet again in the DFB Cup quarter-finals on Tuesday.
Bayern's closest pursuers for much of the last decade, and the last team to wrest the Bundesliga title away from Bavaria - in 2012 - Dortmund have already undergone a managerial change in 2021, with Lucien Favre replaced by academy coach Edin Terzic on an interim basis.
Terzic's man-management style might be different from Favre's, but his tactical set-up is all but identical, with Dortmund, like Gladbach, using a 4-2-3-1, in their case in every single Rückrunde fixture.
Haaland leads the line as he once did at Salzburg, although Marco Reus starts further away from him than Hwang Hee-chan - now of Leipzig - did a few seasons ago at the other Red Bull Arena. That's not to say the Norwegian is either isolated or struggling, though.
Haaland has plundered 27 goals in all competitions this season at a rate of one every 82 minutes he has played. While Gio Reyna was his primary partner in crime earlier in the campaign, Jadon Sancho has recovered the form that saw him contribute a barely fathomable 20 goals and assists in 2019/20, laying on seven assists since the turn of the year, five of which have been for the near-undefendable Norwegian.
Watch: All of Sancho's assists for Haaland in 20/21
Wherever is a light, there is also shadow, though, and Die Schwarzgelben have been a dash more Black than Gold at times this season. Mats Hummels remains one of the sport's pre-eminent quarter-backs, with few equals when in possession, but pace was never his strong suit, which can be difficult in a side with a high defensive line.
It is behind him where the biggest question marks remain, though. Roman Bürki is an excellent outlet with his distribution, but he has only saved 65 percent of the shots on his goal this season. There may be an ongoing debate about whether it's more important for goalkeepers to be adept with their hands or their feet, but since nudging his Swiss compatriot out of the team, Marwin Hitz has saved 74 percent…
So what might the above mean for Rose's Dortmund?
A change away from a 4-2-3-1 seems unlikely, players and coach both familiar with it if not with each other at first. Rose does at least know Haaland from before, and his status as a world-class striker, even at the age of 20, is already secure.
"He's an incredibly positive player," Rose told goal.com in October. "He arrived injured in Salzburg, fought his way up and then took off. At his young age he can already carry a team and he radiates an enormous amount of energy. He's also a funny guy!"
Haaland won't have to do it all on his own, though, at least if Stindl's form under Rose is anything to go by. A 5'11" attacker who might have had more Germany caps if not for injury; only just the wrong side of 30 with plenty still to give; a Borussia captain who plays at No.10? The parallels between Stindl and Reus could scarcely be more pronounced.
Axel Witsel and Julian Brandt - looking to return from injury and the wilderness respectively - might take solace in the experience of Kramer and Neuhaus, meanwhile. And if those two did occupy the double pivot, it would free up Emre Can for use elsewhere…
How better to replicate Elvedi's dominance of possession than to get a trained midfielder to do it? And one who has started 13 of his 24 games this season in the position to boot.
Behind them remains that question about Bürki and Hitz. Switzerland's solution is a certain Yann Sommer…