Los Leones are guaranteed to finish the campaign in fifth place, while the hosts will enter the final day of the season in 16th position.
Match preview
After finishing in 12th and 11th place under Andoni Iraola, Rayo have experienced a drop-off since the 41-year-old opted to swap Vallecas for the English South Coast last summer.
A tumultuous campaign saw Francisco relieved of his duties in February, before Iraola's former assistant Inigo Perez took over the reins to take on the first managerial role of his coaching career.
Perez has won just three of his 13 league matches in charge (D5, L5), but crucially, he has collected enough points to take Rayo's overall tally to 37 and secure top-flight football for another season.
Los Franjirrojos will carry a nine-game winless away run into next season after they suffered a heavy 3-0 defeat in their final away match against Barcelona last weekend.
In contrast, Rayo are currently enjoying a promising spell of home form, having won three of their previous five matches at Vallecas.
However, Saturday's hosts have failed to win their last four home meetings with Athletic since they recorded a narrow 2-1 victory in September 2014.
Athletic's 2023-24 campaign peaked on April 6 when they prevailed in a penalty shootout against Mallorca to win the Copa del Rey for the first time in 40 years.
That memorable night in Seville has ensured that the season will be etched in club history despite the fact they have experienced an inconsistent run of results in the aftermath of their cup success.
Athletic have won two, drawn three and lost two of their seven matches since lifting the Copa del Rey, ensuring they have had to settle for a fifth-place finish rather than Champions League qualification.
Although they fell short in their top-four bid, Ernesto Valverde can still be proud of the fact he has guided the club back into Europe for the first time since he secured a seventh-place finish in the final season of his second spell as Athletic boss in 2016-17.
They may have already clinched Europa League qualification, but Athletic will still be keen to end the campaign with consecutive victories after goals from Raul Garcia and Iker Muniain guided them to a 2-0 victory in their recent home clash with Sevilla.
Los Leones cruised to a 4-0 victory in December's home game against Rayo, which now offers the chance to complete a league double over Los Franjirrojos for the first time since 2015-16.
Rayo Vallecano La Liga form:
W
L
L
D
W
L
Athletic Bilbao La Liga form:
D
L
W
D
L
W
Team News
Rayo midfielder Diego Mendez remains sidelined with an injury issue, while Abdul Mumin and Oscar Valentin are both suspended due to an accumulation of yellow cards.
With the pair set to serve one-match bans, Perez could present starting opportunities to Aridane Hernandez and Unai Lopez.
Club stalwart Oscar Trejo is expected to return to the Rayo lineup after he was forced to miss the defeat to Barcelona through suspension.
Athletic are unable to call upon forward Inaki Williams, who underwent surgery earlier this week to resolve a problem with his left foot.
Gorka Guruzeta is continuing to recover from an appendix operation, while Oihan Sancet is a doubt due to illness.
Muniain is struggling with conjunctivitis and is at risk of missing his final game with the club before he ends his 19-year stay as an Athletic player.
Spain's number one Unai Simon is set to return in goal after Julen Agirrezabala was given the opportunity to play in Athletic's final home match of the season.
Rayo Vallecano possible starting lineup:
Dimitrievski; Balliu, Lejeune, Hernandez, Espina; Lopez, Ciss; Palazon, Trejo, Garcia; Camello
Athletic Bilbao possible starting lineup:
Simon; De Marcos, Vivian, Alvarez, Berchiche; De Galarreta, Prados; Berenguer, Gomez, N Williams; Villalibre
We say: Rayo Vallecano 1-1 Athletic Bilbao
Athletic will enter Saturday's contest as the favourites, but they have found victories hard to come by in recent away games, having won just one of their previous four road trips.