Dani Olmo is finally in line to make his Barcelona debut against Rayo Vallecano on Tuesday with a temporary registration set to be approved by LaLiga, sources have confirmed to ESPN.

Olmo, a 55 million ($61m) arrival from RB Leipzig, has missed Barça's first two matches of the season because his registration has not been processed with LaLiga due to the club's continued financial woes.

Sources told ESPN on Monday that it was unlikely he would be available to face Rayo, either, but a long-term injury suffered by Andreas Christensen will free up cap space to register new additions.

Article 77 of LaLiga's Regulations for the Preparation of Budgets allows clubs to exceed their spending limit in the event a player in the squad is ruled out for a substantial period of time.

Barça have sent medical reports to LaLiga detailing that an Achilles problem will sideline Christensen for up to four months, allowing them to use 80% of the Danish centre-back's salary towards registering another player in the meantime.

Sources have confirmed that gives Barça enough room to register Olmo before Tuesday's game, although the final paperwork still needs to be cleared.

Barça had begun to make moves to register Olmo with a series of outgoings. Ilkay Gündogan, Vitor Roque, Mika Faye and Clément Lenglet are among those who have left the club over the last week, although it was still not enough to inscrive Olmo.

The Spain international, who played for Barça's academy until he was 16 before leaving for Croatia, will be granted a registration until Dec. 31.

One source says Barça hope it will prove a temporary measure and that their business before the end of the transfer window will also allow them to have Christensen and Olmo both registered properly before January.

It is not the first time Barça have recurred to Article 77 to register players.

They used the same formula last winter with Vitor Roque, using Gavi's injury to temporarily force through the registration of the Brazilian striker, who joined Real Betis on loan on Monday.

Barça also used Article 77 earlier this month to ensure centre-back Iñigo Martínez was registered for the start of the season, with Ronald Araújo the injured player whose salary space could be utilised.

All clubs in Spain are subject to a spending cap which is roughly determined by the difference between a team's revenue minus non-sporting outgoings and debt repayments.

Barça's had dropped to just over 200m ($223m) earlier this year, with LaLiga due to announce the new limits after the transfer window closes this week.

Until Barça are operating within their cap, the only way they can register players is by reducing the wage bill, raising transfer fees or bringing new revenue streams into the club.

Sources say the club's goal before the transfer window closes is to return to LaLiga's 1:1 rule, a regulation which would allow them to spend 100% of anything they save or raise.

While they remain in breach of their cap, they can only spend a percentage of any savings, with the percentage, rarely greater than 50%, determined by the size of the saving.