Valencia snatched top spot in the Primera Liga on Saturday thanks to a 3-2 home win over Real Zaragoza, while champions Real Madrid slipped to second after a barely deserved 1-1 draw at dominant Osasuna.
Ronaldo saved the day for Real with a 74th-minute strike to cancel out a top-class finish from Ivory Coast striker Ibrahima Bakayoko, who had put the Navarrans ahead early in the first half.
Valencia made a great start at the Mestalla as they stormed to a 3-0 halftime lead against Zaragoza, with neatly crafted goals from wingers Jorge Lopez and Vicente, and gifted Argentine playmaker Pablo Aimar.
But Zaragoza hit back with well worked strikes from centre forward David Villa and midfielder Cani and the Mediterranean side had to endure a nervous last 10 minutes to hold on for victory.
The results left Valencia and Real level on 27 points, but Rafa Benitez's side lead the table on goal difference.
Their reign at the top may turn out to be short-lived, though, as third-placed Deportivo Coruna, who are only a point behind, could leapfrog both teams if they beat Villarreal on Sunday.
Atletico Madrid moved up into fourth place a further four points back after notching their sixth victory in seven matches with a 2-0 win over Malaga at the Calderon, while Osasuna climbed to fifth.
Real Madrid, who made the trip north without injured midfielders Zinedine Zidane and Luis Figo and defender Roberto Carlos, began with Esteban Cambiasso and Guti in the centre of midfield, while David Beckham reverted to his former position on the right flank.
But they never looked comfortable at a packed El Sadar and it was Osasuna who were the first to show when Bakayoko controlled a flying cross with his back to goal, swivelled and volleyed just over the bar on five minutes.
Real failed to heed the early warning, though, and six minutes later the former Olympique Marseille player put the Navarrans ahead with a cool finish.
Receiving the ball on the edge of the area from fellow striker John Aloisi, Bakayoko checked inside Ivan Helguera and fired the ball past Real keeper Iker Casillas with a fierce left-foot finish.
The champions recovered their nerve a little on the half hour mark when Ronaldo produced a couple of his trademark jinking runs that provided the first threats to the Osasuna defence.
But it was Osasuna who continued to dominate as they poured through the middle and tormented the Real defence.
The Navarrans manufactured a host of further scoring chances but the Primera Liga's leading scorer Ronaldo made them pay when he equalised 16 minutes from time to take his season's tally to 10 goals.
David Beckham, who was back in the middle in the second half, threaded a perfect through pass to the feet of the Brazilian who sprinted past one defender, fended off another and tucked home inside the near post.