An Inaki Williams 90th minute own goal gives Athletic Bilbao all 3 points.
Sevilla lost 1-0 to Athletic Bilbao at home on Monday, dealing a near-fatal blow to their La Liga title hopes.
Athletic counter-attacked and striker Inaki Williams displayed the courage to raise the ball into the top corner, dealing a late body blow to Julen Lopetegui's foot.
The goal handed Sevilla their first loss since March 6 and ended a five-game winning streak in La Liga, which had placed them among the title contenders.
With four games remaining, Sevilla is fourth in the table with 70 points, four points behind second-placed Real Madrid and third-placed Barcelona, and six points behind leaders Atletico Madrid.
Coach Lopetegui thought his team had been treated unfairly and was enraged that a penalty was not awarded when the ball hit the hand of Athletic defender Mikel Balenziaga early in the second half.
"We could easily have been awarded a penalty, we didn't have any luck," he told reporters.
"We have won many games with far fewer chances than we had tonight. But we have earned the right to dream of the title and we'll keep going."
When Sevilla travels to Real Madrid next weekend, they will have a chance to claw their way back into contention.
Athletic won their second game in eight days against a title challenger, after defeating Atletico Madrid 2-1 at home last Sunday.
When they host Real Madrid on May 16, the Basques will have another say in the title race.
"It's a very tough blow. We tried everything, we had a lot of chances and then they had one opportunity and scored," added Sevilla captain Navas.
"But we're going to keep on trying, we're going to fight in every game and we're going to Madrid next week to win."