Faced with a team that had all but ended their hopes of winning the title in 2010-11 and the same side which had inflicted a similarly painful defeat on Barca earlier this year, the red of Osasuna spelt real danger for Jose Mourinho's Madrid on Saturday evening.
But Real responded with a show befitting of the meanest of matadors.
In a week marked by the controversy concerning Catalan complaints over the quality of the playing surface in Milan by Barca, Madrid were faced with a potato-patch pitch in Pamplona. But unlike their fiercest foes, they didn't complain.
As Ronaldo attacked down the worst-affected part of the field at the Reyno de Navarra, one wondered if he might have to wait until the second half to make an impact. The Portuguese put paid to such thoughts, however - and he did so very quickly with a brilliant run down the flank and left-footed cross for Karim Benzema at the far post, from where the Frenchman beat Andres Fernandez with an outrageous volley a la Van Basten to open the scoring.
It was a goal that would have graced any game and was vital in that it allowed Madrid to take control of a match many had tipped them to lose. But there was more. Ronaldo raced forward and came within inches of making it two with a dipping drive which dropped just the wrong side of the crossbar in Madrid's next foray. The Portuguese attacker was in the mood.
Cristiano continued to try his luck from distance and unleashed an unstoppable thunderbolt of a shot with his right later in the half from fully 40 yards which left Fernandez beaten and Osasuna on their knees as Madrid went two up. The 27-year-old's stunning strike owed as much to prime physical preparation as it did to tremendous technique and Ronaldo, jubilant, celebrated by showing off his impressive thigh muscles to the watching world.
Gonzalo Higuain was not to be denied, either, and the Argentine made it 3-0 moments later as he latched on to a Xabi Alonso pass and chipped Fernandez to score his 100th goal for Madrid. And after Ronaldo's deflected free-kick had made it 4-1 following Nino's header shortly after the interval, Higuain made it five for Madrid with his 20th league goal of the campaign - and his side's 100th in just 30 Liga fixtures - as he headed home another Cristiano cross from the left.
While Mourinho waxed lyrical about his side's showing in the Osasuna press room, Barca struggled to break down Athletic Bilbao at Camp Nou. After Thiago's early strike was correctly ruled out for a marginal offside decision, the Catalans had to wait until five minutes before the interval to make the breakthrough as Andres Iniesta raced on to a Lionel Messi pass, steadied himself and lashed a venomous drive past Gorka Iraizoz from close range.
Iniesta, seldom prolific but always influential, has a knack of popping up with important strikes - and this one was no exception as it saw Barca move in front in a match proving more difficult than expected. And they stayed there, thanks to Messi's second-half spot kick which was highly contentious but which put some gloss on a performance lacking in sparkle against an Athletic side in action just 48 hours prior to this match versus Schalke in the Europa League.
Both sides had efforts cleared off the line, while Seydou Keita and Pedro came very close for the Catalans late on, but the job was done and Guardiola's side can now switch their attentions back to the Champions League and the second leg of their quarter-final tie against AC Milan on Tuesday.
Madrid are in action on Wednesday against APOEL in their own quarter-final second leg, having claimed a 3-0 win in Cyprus last week. But then it's back to La Liga, with three more fixtures for the top two ahead of the Clasico clash at Camp Nou on April 22.