A 2-1 win over already-relegated Real Betis for Osasuna at El Sadar was not enough to safeguard the club's top-flight status and was marred by a barrier collapsing behind one of the goals, causing numerous home fans to spill on to the area of the pitch beyond the advertising hoardings.
Oriol Riera gave Osasuna a 12th-minute lead with a neat finish, but the game was then suspended for over half-an-hour as the barrier gave way during the home fans' celebrations.
Security officials removed the remainder of the barrier and the league authorities subsequently delayed all other matches for 35 minutes at half-time to ensure the crucial relegation deciders finished at the same time.
Less than a minute after play was restarted, Javier Acuna doubled their lead as Osasuna targeted a win and simultaneously hoped either Getafe or Granada lost.
Betis pulled one back through Javi Chica's curling finish 19 minutes from time and, although the hosts held on to the win, Osasuna ultimately dropped out of La Liga after Granada won 1-0 at Valladolid and Getafe beat Rayo Vallecano 2-1.
Granada's victory came courtesy of a 44th-minute Stefan Mitrovic own-goal, moving them on to 41 points, just out of Osasuna's reach, while Valladolid slip down to La Segunda alongside Javi Gracia's side.
Getafe, meanwhile, registered a 2-1 win at Rayo, who themselves look set for a close-season of upheaval, with most of their squad reportedly out of contract in June. A Ciprian Marica brace proved decisive for Getafe.
Athletic Bilbao ended an impressive campaign with a 0-0 draw at Almeria, while Villarreal pipped Real Sociedad to sixth place after beating them 2-1. Giovani dos Santos and Ikechukwu Uche put Villarreal two goals to the good before Carlos Vela pulled one back in stoppage time.
In the season's last match, a much-changed Sevilla side beat Elche 3-1 at Estadio Ramon Sanchez Pizjuan, rounding off a good campaign for Unai Emery's men after their penalty shoot-out success against Benfica in the UEFA Europa League final on Thursday.
Two goals from Vicente Iborra, either side of Jairo Samperio's fourth Liga strike of the season, put the hosts in a commanding position going into the final stages, despite a host of key players sitting out.
Juventus-owned forward Richmond Boakye netted late on for Elche, but it was nothing more than a consolation.
Fran Escriba's men end the season 16th, while Sevilla finish fifth.