Sporting director Ole Book has had an eventful few days at the club.
Summer signing Giannis Konstantelias ruptured his anterior cruciate ligament on Saturday, and by Monday evening it appeared Dortmund had found his replacement in 19-year-old Marcel Regula, with Polish media reporting an agreement between BVB, the player and his club Zagłębie Lubin.
That deal was indeed close, but Dortmund ultimately opted instead for a season-long loan of Arsenal's Ethan Nwaneri, 19, on transfer deadline day.
According to Sky, the trail to Regula could still heat up again. The Polish youth international would become a candidate for Dortmund once more if Arsenal are able to trigger a clause to cut short Nwaneri's loan next winter. He is described as a "hot alternative" in the report, though any move would need to be renegotiated from scratch, with a fee of around €8m previously on the table.
Konstantelias, a Greek international who had only just arrived at the club this summer from PAOK, scored on his Bundesliga debut before suffering the serious injury that will keep him out for several months. Dortmund moved quickly to bring in cover, with Nwaneri arriving on loan for the season without any option to buy, taking over his full salary from Arsenal.
Regula, an attacking midfielder capped by Poland at Under-17, Under-19 and Under-21 level, has established himself as a regular for Zagłębie Lubin in the Ekstraklasa this season, having previously been on Dortmund's radar since early August. Should Nwaneri's loan end prematurely in January, Regula would give Dortmund a ready-made alternative to reopen negotiations with.
Nwaneri arrives in Germany having spent the second half of last season on loan at Marseille, where he scored twice in nine Ligue 1 appearances after struggling to make an impact in France. He remains under contract with Arsenal until 2030 and has made 51 first-team appearances for the Gunners since making his debut aged just 15, scoring 10 goals along the way. Dortmund had previously explored a move for the England Under-21 international earlier in the summer without reaching an agreement, before Konstantelias' injury reopened the door to a deal.