By Andy Hall at the Santiago Bernabéu
A breathtaking four-goal second-half burst put Real Madrid CF on course for their fifth appearance in the semi-finals of the UEFA Champions League in as many seasons after the Spanish champions turned the tables on a resolute AS Monaco FC side who led 1-0 at half-time.
Sébastien Squillaci bundled in a loose ball on 43 minutes to give the French side the lead, but Madrid upped the tempo after the break and once Iván Helguera had pulled them level six minutes after the restart, the home side took control in stunning fashion - although a late Fernando Morientes header might yet prove significant.
Coach Carlos Queiroz welcomed Ronaldo back into the side as Madrid looked to break a sequence of three matches without a win since Zinedine Zidane's goal two weeks ago took them through to the last eight at the expense of FC Bayern München. Santiago Solari made way, while Raúl Bravo started in place of the suspended Roberto Carlos.
Morientes, on loan at Monaco from Madrid, started up front for the French club alongside captain Ludovic Giuly, preferred to Dado Pršo after missing the first knockout victory against FC Lokomotiv Moskva through injury. Squillaci and Edouard Cissé both shook off knocks to start in place of Hugo Ibarra and Shedi Adebayor.
Both teams created good opportunities during an evenly-balanced first half. Zidane skewed his effort wide of Flavio Roma's post four minutes into the game then, at the other end, Morientes fed Cissé whose centre just failed to reach Giuly. The early exchanges prompted a wave of end-to-end action. Zidane's centre was headed narrowly over by Raúl González then Ronaldo, supplied by Luís Figo, saw his header rebound for a corner amid appeals for handball.
Off the line
While Monaco looked comfortable in possession, it was Madrid who created the most danger. Raúl went close again on the quarter-hour, once more directing his header over, then Zidane had the ball whipped from his feet as he prepared to shoot. Madrid, with injury-hit defender Bravo temporarily off the pitch, had a fright when Giuly glided past Iker Casillas, but his attempt was cleared off the line by Míchel Salgado.
Bravo makes way
Bravo was replaced on 28 minutes by Francisco Pavón and Monaco tried to take advantage of Madrid's defensive reshuffling, Jérôme Rothen testing Casillas from distance. But the home team should have taken the lead moments later, Figo sweeping a cross into the area on 32 minutes which an unmarked Ronaldo headed wide from three metres.
After Madrid's most sustained period of pressure Monaco came alive. Giuly stole the ball off Zidane in the centre and raced goalwards. His effort was parried by Casillas, but from the resulting corner Squillaci pounced on a loose ball to put the visiting side ahead.
Madrid hit back
Monaco's lead was short-lived as Madrid turned the screw early in the second half. From David Beckham's corner Helguera headed in to equalise and Zidane made it two on 69 minutes when he turned in the rebound after Roma had saved well from Figo.
Figo adds third
Seven minutes later the Portuguese international added the third, heading in a rebound off his own penalty after Ronaldo had been hauled down in the area. The Brazilian then crowned his return with the fourth on 81 minutes. A header from Morientes narrowed the score seven minutes from time, but Madrid - who will be without Beckham for the second leg after the midfield player collected a last-minute booking - had already sounded their warning.