
Marcelino’s men are chasing a UEFA Champions League place and closed the gap on Bilbao, who drew 1-1 against Real Madrid on Sunday, to three points in La Liga.
Jeremy Perbet and Manu Trigueros struck in a nine-minute spell just after half-time before the former completed his brace.
Osasuna scored a consolation goal in the 87th minute, but Riera’s effort was undoubtedly the pick of the goals.
Riera beat his marker to Emiliano Armenteros’ cross and watched his back-heel float in off high off the back post.