Osasuna, the bottom side in La Liga, gave themselves breathing space at the expense of Espanyol, who wasted a chance to climb out of the relegation zone, and brought their four game unbeaten run to an end.
'Los rojillos' put their faith in playing an organised game, keeping solid defensive lines and taking no risks, and in doing so bought some more time for under fire coach José Luis Mendilibar.
The game was played in a frantic mode from the off, with Armenteros and Cejudo leading the line for Osasuna, and Verdú and Sergio García in charge of lifting the crowd at Cornellá-El Prat, making for a direct, intense and dynamic game of football.
Cejudo gave the Navarrans the lead on 21 minutes from a corner, with the Espanyol defence failing to react to a second attack once they had cleared the initial danger.
Mauricio Pochettino's side appeared stunned by the goal but Osasuna failed to take advantage of their imprecision. Espanyol created a flurry of chances as half-time approached, with Verdú missing two golden chances and Victor Sánchez another.
Espanyol continued their search for an equaliser after the re-start, with Longo striking the bar after 59 minutes and Verdú hitting a post just two minutes later. But they were punished for their adventures and the visitors launched a counter attack, with Cejudo finding Kike Sola, who rounded two defenders and goalkeeper Cristian Álvarez to make it 2-0.
Mendibilar's side then chose to sit back, demonstrating great discipline, albeit little presence up front. Nonetheless, Omwu rounded off proceedings after a pass from Armenteros to kill the game, leading many home fans to leave the stadium in droves, while others struck up chants in protest at their dire situation.