Joaquín Caparrós’ side were already nervously looking over their shoulders, with the five-point gap between themselves and LaLiga's bottom three seemingly far too close for comfort.
The Andalusians had an early chance when Diego Hormigo flashed an angled attempt wide, but those hoping this would spark a flurry of goalscoring chances would be left disappointed in a largely cagey opening 25 minutes.
However, the contest dramatically sparked into life courtesy of Rubén García’s superbly struck free-kick from a tight angle which flew past Ørjan Nyland. It was the 31-year-old’s fourth goal of the season and a second in the space of five days, after finding the net in a 3-2 win over Real Valladolid last Sunday.
As if that wasn’t enough, Sevilla’s frustration was further compounded just past the half-hour mark, when Dodi Lukébakio was shown a straight red card for elbowing Alejandro Catena, meaning the Belgian would not end his six-game goal drought this evening.
Referee Adrian Cordero then initially evened up the numbers when he harshly gave Pablo Ibáñez his marching orders for a challenge on Djibril Sow, but this was subsequently downgraded to a yellow card following a VAR review.
Boosted by that let-off, Los Rojillos began brightly after the restart, and an eye-catching cross from the outside of Bryan Zaragoza’s right foot picked out Ante Budimir, who headed wide.
Chances were few and far between for the visitors, but Lucien Agoumé should have restored parity when he headed wide from a corner at point-blank range.
That Agoumé chance aside, Vicente Moreno’s men were looking largely comfortable, and Zaragoza almost found a second for the hosts with a speculative right-footed strike which flew just past the post.
Ultimately, García’s delightful set-piece would prove to be the difference in Pamplona, leaving seven-time UEFA Europa League winners Sevilla with the unthinkable prospect of a relegation scrap heading into the final five games of the season.
Caparrós’ men slip down a place in the table to 16th, while Osasuna continue their dreams of competing in the main stage of a European competition for the first time in 19 years and move up three places into eighth.
Flashscore Man of the Match: Rubén García (CA Osasuna)