After their sensational comeback against Manchester City in midweek, Carlo Ancelotti rested key players ahead of the looming second leg.
With LaLiga’s top three separated by just two points, his side could not afford a slip-up here, and the league leaders got off to a positive start by opening the scoring on the quarter-hour mark.
Following a spell of possession, Federico Valverde powered down the right flank, before his low cross was met with a first-time finish into the roof of the net by Kylian Mbappe.
Clearly in no mood to end their unbeaten run that easily, Osasuna came close to an equaliser near the half-hour mark, when Aimar Oroz collected the ball in the box and drilled a finish on goal, only for Thibaut Courtois to turn it around the post.
Madrid were then dealt a blow five minutes before half-time after Jude Bellingham was shown a straight red card.
His sending off wasn’t for a foul, but instead for apparent dissent towards the referee, giving Los Blancos a tough task for the remainder of the afternoon.
The home side came flying out for the second half, and they were given an opportunity to equalise just before the hour mark.
Ante Budimir was first to react to a rebound in the box, but the striker was brought down after his follow-up by Eduardo Camavinga - a decision which left the Madrid players and bench incensed, following weeks of refereeing controversy.
Budimir picked himself up and tucked the penalty away to draw his side level.
Now level and a man down, Madrid seemed content with holding on for a point, sitting back and aiming to hit on the counterattack.
There was little goalmouth action in the final moments as the points were shared, and with Ancelotti’s men failing to win, the onus is now on Atletico Madrid and Barcelona ahead of their respective fixtures this weekend.
Both sides have the opportunity to climb above Los Blancos, while Osasuna move up into seventh place ahead of this weekend’s remaining fixtures.
Flashscore Man of the Match: Federico Valverde (Real Madrid)