Dani Olmo was forced to miss Saturday's LaLiga clash against Athletic Club after Barcelona lost their race to have him registered in time for the fixture.
Olmo, 26, joined Barça from RB Leipzig for an initial €55 million ($61.6m) earlier this summer but his inscription with the league has not yet gone through due to the club's continued financial woes.
Barça remain in excess of their league-imposed annual spending limit -- a cap which all Spanish clubs have and is roughly determined by the difference between a team's revenue minus non-sporting outgoings and debt repayments -- and must reduce the wage bill and/or increase revenue to register new additions.
As a result, Olmo missed the opening-day win against Valencia last weekend.
He has been named in the squad to face Athletic, with Barça previously his inclusion was "pending the player registration being completed with LaLiga."
Barcelona went onto beat Athletic 2-0 but asked afterward whether Olmo would be registered in time for the club's next match, against Rayo Vallecano on Tuesday, coach Hansi Flick responded: I don't know. Of course I hope so. These things we have to accept because we can't change it. We know it's not easy when we signed here, but focus on what we want to do. Today we wanted to win 3 points and did it."
Barça were working on a series of outgoings in an attempt to ensure Olmo is available for Flick on Saturday.
Ilkay Gündogan's departure to Manchester City has already been confirmed, while Clément Lenglet, Mikayil Faye and Vitor Roque are all close to leaving, too.
Sources confirmed to ESPN that Lenglet will sign a contract extension until 2027, spreading his remaining salary over two years instead of three, before going on a season long loan to LaLiga side Atlético Madrid.
Defender Faye is set to join French side Rennes for an initial €14m as part of a deal that includes various add-ons and clauses which would allow Barça to re-sign the young Senegal international in the future.
Roque, meanwhile, will join Real Betis on loan after failing to secure a place in Barça's first team following his €35m transfer from Club Athletico Paranaense in January.
Elsewhere, midfielder Fermín López makes the Barça squad for the first time this season after returning from some time off following success with Spain at the European Championships and the Olympic Games this summer.
There is no Andreas Christensen, though, who has an Achilles problem and is set for several weeks on the sidelines.
"I think he cannot help the team [at the moment] and he knows that," Flick said in a news conference on Friday. "Last year, he made many games only 60 minutes with problems. Now we take care of that."
Barça are also without long-term absentees Ronald Araújo, Gavi, Frenkie de Jong and Ansu Fati.