Michy Batshuayi, Marco Reus and Jadon Sancho are all included in Borussia Dortmund's Europa League squad, but defender Manuel Akanji misses out on a place.
UEFA regulations allow clubs to register three new players for the knockout rounds of the competition, but only one can have been fielded in a UEFA club competition group stage match for another club.
That meant BVB had to choose between on-loan Chelsea striker Batshuayi and Akanji, signed from Basel, who had both played in the Champions League this season.
Coach Peter Stoger opted to register Batshuayi as well as England youth international Jadon Sancho and Germany international Marco Reus, who is set to return from injury later this month.
Meanwhiel, former Dortmund player and coach Matthias Sammer has said the club are no longer chasing Bayern Munich and lack a leader on the pitch following the exodus of star names including Ilkay Gundogan, Pierre-Emerick Aubameyang and Mats Hummels.
"Dortmund's reality no longer is Aubameyang or Dembele, and right now also not Marco [Reus] because he is injured," Sammer said in his role as a pundit for broadcaster Eurosport.
"The reality is [Alexander] Isak, [Jadon] Sancho and [Christian] Pulisic. Their average age is 18.
"Dortmund must think more about the team leaders in the future. Some of the transfers, like Mats Hummels, really hurt them.
"Dortmund are currently no longer chasing Bayern -- it's rather more realistic they are chasing a top-four finish."
Ahead of Dortmund's match at bottom of the table Cologne on Friday, BVB are sixth in the Bundesliga, three points behind second-placed Bayer Leverkusen.