Carlo Ancelotti rested Karim Benzema before the mid-week Champions League clash at Liverpool as Madrid, also without Toni Kroos, struggled to victory at El Sadar.

Chances were limited without top scorer Benzema but Valverde's calm finish after 78 minutes and Asensio's similarly cool strike in stoppage time secured a vital win in Madrid's title defence.

Victory moved Los Blancos five points behind Barca before Xavi's side hosts Cadiz on Monday (AEDT).

Sergio Herrera thwarted a glorious Vinicius Junior chance after an errant Jon Moncayola pass while Thibaut Courtois parried away from Moi Gomez in an entertaining opening.

Valverde whistled a long-range attempt narrowly off target before Ante Budimir whipped the best first-half opportunity just wide from the edge of the area.

A resurgent Madrid twice went close to breaking the deadlock after the interval.

Rodrygo had Herrera scrambling with a curling effort that evaded the bottom-right corner and Vinicius' cool finish was denied for offside from David Alaba's throughball.

Osasuna responded as Gomez struck the right post with a driven effort through a crowd of Madrid defenders before Moncayalo volleyed narrowly wide with Courtois static.

Madrid finally edged in front against its mid-table opponent as Vinicius crossed for Valverde to coolly poke into the bottom-right corner.

Asensio sealed victory in the closing stages with a deadly finish past Herrera after Alvaro Rodriguez's selfless pass.