On Thursday, Timo Horn went under the knife in order to solve a knee injury and is expected to be timetabled for a return in January.
The 1. FC Köln goalkeeper - who was reportedly having trouble with his meniscus, per kicker - will be a big miss for the Billy Goats.
Given Horn's standing in the side, it certainly won't be an easy job to replace the 23-year-old shot-stopper.
Stöger has his say
"We're sorry for the player," head coach Peter Stöger told kicker on Thursday Horn had been enjoying a superb start to the season with Köln ridding high in Bundesliga.
He added, "Everyone involved in the training sessions improves our quality because the competition for places is different, but we have enough guys who can cover."
Stöger concluded, praising the depth and resilience of his side: "We have a squad, which is quite balanced. We will not whine."
Horn will now join centre-back, Dominic Maroh and wing wizard, Leonardo Bittencourt on the sidelines. The Billy Goats are unlikely to see either back before Horn.
With the Rhine Derby coming up against Borussia Mönchengladbach, they will be hoping to put further distance between themselves and the faltering Foals.
Will it be Kessler or Müller?
The decision as to who will take Horn's place in between the sticks, according to Stöger, will be left to goalkeeping coach, Alex Bade.
Given that 20-year-old Sven Müller, the regular 'keeper for the Regionalliga West side, stepped up and kept two clean sheets, he seems set to grab the gloves.
Thomas Kessler offers a more experienced option, though Müller was more than competent against BFC Preussen and VfL Wolfsburg.
The former Germany under-15 international has made seven appearances across both sides and kept five clean sheets in seven games, including both first-team matches.