Depor needed a win to have any chance of staying in the second tier of Spanish football, but the match was called off not long before kick-off on Monday after a number of Fuenlabrada players tested positive for coronavirus.
The decision caused controversy as final-day matches are usually played at the same time.
Relegation rivals Albacete won 1-0 at Cadiz while Numancia prevailed 2-1 against Tenerife, meaning Depor were seemingly consigned to the drop despite having a fixture still to play.
Depor released a statement in which they made clear the issue has been raised with LaLiga and the Royal Spanish Football Federation (RFEF), adding that the "competition and the spirit of the last two days have been corrupted with matches whose results influence others".
"Of course, we are in full agreement with the reasons that force the suspension and that are assumed by this club, but we consider that it must be understood that Fuenlabrada has not shown up for the match and that Deportivo is harmed by the dispute the rest of the day in these conditions," the statement continued.
"For all this, the Real Club Deportivo de La Coruna will study and take all the necessary legal actions, before the corresponding instances, in defense of its legitimate interests."
Depor slipped out of LaLiga at the end of the 2017-18 campaign. It is only 20 years since they were top-flight champions, as well as winning the Copa del Rey in 2002 and reaching the Champions League semi-finals in 2004 during what was a golden era for the club.
Rayo Vallecano, who were aiming to try and seal a play-off spot but finished the season outside the top six, released a statement prior to their game to "express their deepest outrage at the adulteration of the competition".
Elche are in the final play-off spot as it stands but are only one point clear of Fuenlabrada.
The final-day fixture in the second tier was cancelled just hours before kick-off last month after several Fuenlabrada players tested positive for coronavirus.
Controversially, the remaining matches in the division went ahead and results elsewhere meant Depor were seemingly consigned to the drop despite having a game to spare, while Fuenlabrada were left hovering outside the play-offs.
Depor threatened to take legal action after the game was cancelled, while they requested the annulment of the results from the last round of fixtures and the suspension of promotion and relegation.
It was reported that an investigating judge looking into the postponed clash and suggested the match should not take place as Fuenlabrada know the results of their rivals, which would have meant Elche took the final play-off spot.
However, the RFEF announced on Monday its competition committee had ruled the game will take place this week, meaning Fuenlabrada can still extend their campaign. The play-offs begin on August 13.
In a short statement, Fuenlabrada welcomed the ruling, saying: "We consider that justice has been done by being able to finish the competition on the field, something that we will do with the greatest enthusiasm."
Reinier, 18, joined Madrid from Flamengo for a reported €30million in January and played for the Castilla side in the Segunda B1.
He made just three appearances under Raul before the season was put on hold amid the coronavirus pandemic.
The Brazilian will spend the next two campaigns in the Bundesliga with Dortmund, who have built a reputation for developing young talents by providing first-team opportunities.
Reinier said: "I am happy to be with BVB now. The club is known for betting on young players and making them better.
"I want to learn a lot here, play a lot and help the team to be successful. I hope that we will have many happy moments together."
Reinier, who won the Campeonato Brasileiro and Copa Libertadores with Flamengo in 2019, had been training with Zinedine Zidane's team.
"Reinier is a player who brings enormous talent and can be used in various attacking positions," said Dortmund sporting director Michael Zorc.
"We have been watching the boy for more than two years. He has great technical skills as well as good physical strength.
"After a long break from competition we will give him the time he needs to get used to German professional football. He will then be an additional option in attack."
Achraf Hakimi spent two years on loan at Dortmund from Madrid but opted to join Inter for a reported initial fee of €40m when his spell at Signal Iduna Park ended.
