|Both sides had plenty of chances but the result means that Real are now just four points above rivals Barcelona with seven games remaining [EPA]
Real Madrid's bid for their first Spanish league title in four seasons received another setback on Sunday after the leaders slipped to a 0-0 home draw with Valencia.
Madrid's third draw in five matches had cut their commanding 10-point lead over defending champions Barcelona to four with seven rounds to play.
Barcelona piled the pressure on with a 4-1 win at Zaragoza on Saturday, and Madrid failed to respond as Valencia came close to scoring with two shots that hit the goal-frame in a high-tempo thrilling match that should not have ended scoreless.
Valencia goalkeeper Vicente Guaita ensured the good result for the visitors with a series of superb saves late on, including denying Angel Di Maria deep into stoppage time.
"We knew it was important to hold off their counterattack and get out on the break ourselves,'' said Guaita.
"The entire team made an excellent effort.''
Madrid's stumble places further importance on their visit to Barcelona's Camp Nou in three rounds' time.
The struggling pacesetters visit cross-town rival Atletico Madrid on Wednesday and then welcome last-place Sporting Gijon before the sixth "clasico'' match of the season that could go a long way to deciding the title.
"Without a doubt, we expected to win the three points because each point is fundamental,'' Madrid midfielder Xabi Alonso said.
"We still have the advantage, not what we had before, but we have to go forward.''
The result also stopped Madrid one game short of setting a club record of scoring in 42 straight games.
Even though Valencia entered the march 30 points behind Madrid in the table, the team lived up to their third-place standing by putting up a spirited fight despite having top-scorer Roberto Soldado limited to the final 15 minutes due to physical problems.
Cristiano Ronaldo had the first scoring chance eight minutes in when he let loose a blistering long-range blast that rattled the woodwork.
Moments later, Valencia forward Sofiane Feghouli almost connected with a shot from outside the area as the visitors also showed some bite early on.
Saturday 7 April
Getafe 2-0 Sporting Gijon
Rayo Vallecano 6-0 Osasuna
Espanyol 2-2 Real Sociedad
Zaragoza 1-4 Barcelona
Real Betis 3-1 Villarreal
Sunday 8 April
Levante 2-0 Atletico Madrid
Mallorca 0-0 Granada
Athletic Bilbao 1-0 Sevilla
Real Madrid 0-0 Valencia
Ronaldo enjoyed another opportunity in the 19th thanks to Karim Benzema's back-heeled pass, only to see his low shot saved by Guaita.
But Valencia continued to attack, with defender Ricardo Costa heading against the post with goalkeeper Iker Casillas flat on the ground after having parried Tino Costa' long-range strike in the 25th.
Madrid coach Jose Mourinho sent on Di Maria for striker Higuain Gonzalo at halftime, and the Argentina winger wasted no time in sliding a ball through for Ronaldo to force a one-handed save from Guaita.
Valencia hung tough with the European powerhouse, and Tino Costa again made the home crowd gasp when he blasted against the top corner of the goal frame in the 55th.
As Madrid's nerves began to show, Valencia looked to take advantage of their opponents runs forward with speedy reinforcements Pablo Hernandez and Jeremy Mathieu, who missed with a long-range shot just after Ronaldo tripped on the ball with only the 'keeper to beat.
Madrid charged forward with Kaka on as a substitute, and Guaita had to stop Di Maria's shot and make an excellent pair of reflex saves to repel back-to-back attempts by Benzema from close range in the 78th.
Di Maria had another chance to grab the win just before the whistle, but Guaita again was there to smother his low strike.