If they win the title this year, this is the peak of their modern existence. They've captured lightning in a bottle this year, but within a year of Xabi leaving they will be back to competing for a Europa spot. Dortmund and Leipzig will be stronger. Leverkusen are five times runners-up having never won it, and haven't even been finished in that position for 13 years. Their best success was finishing second for a handful of years in the late 90s and early 2000s. This isn't a historically top club.

Not sure what the league parity or Leverkusen supporter feelings have to do with this - it's a business. Xabi knows this, Leverkusen knows this and Bayern knows this. I think it's far more likely that Bayern sign Xabi than they do Wirtz (unless Gnabry and/or Coman move, then all bets are off).

Certain players/managers have connections with their clubs and supporters which make it an integral part of their success. That's why Jurgen Klopp said he'll never manage a club in England again. I'm not saying Xabi won't ever coach Bayern - he very well might - but I don't see him doing it directly and raiding the squad. Just my hunch.

As for Leverkusen, I've been impressed by Xabi of course. But I'm also impressed by their business of recent years. Grimaldo on a free was absolutely stunning. You can attribute it to Alonso, but deals involving Havertz, Diaby and sales along with arrivals of Frimpong, Wirtz, Schick, Tapsoba, etc all before Alonso show a fairly shrewd business. So just like Brighton "survived" Potter, I think Leverkusen have a chance to survive losing Xabi. Afterall, the guy that took a chance with Xabi will still be the sporting director.