Saturday turned out to be a day of surprises in the Spanish Liga, with twin giants
Barcelona and Real Madrid both suffering shock defeats, dpa reported.
Barca crashed 2-1 at Real Sociedad, despite enjoying 80 per cent possession, Real went down 3-2 at home to lowly Zaragoza - with Angel Lafita sinking the whites with two goals.
Both giants looked tired after Wednesday's stormy Champions League clash between the two teams, which Barca won 2-0 in Madrid - and after all the controversy and acrimony surrounding that game.
Sociedad and Zaragoza are practically safe after their surprise wins.
Barca's second league defeat leaves them with 88 points from 34 games, eight more than Real, and four points away from their straight league title.
Youngster Thiago gave Barca the lead on the half hour with a precise lob, after a good move between Xavi and Lionel Messi.
The visitors seemed to be cruising towards another pleasant win, but supersub Diego Ifran made it 1-1 18 minutes from time with a cool finish.
Barca defender Diego Milito had a goal wrongly disallowed for offside, then Javier Mascherano committed a clumsy penalty which was converted by Sociedad's Xabi Prieto.
Earlier on Saturday, Real had flopped for the fourth consecutive home match. The defeat against Zaragoza was more bad news for coach Jose Mourinho, who is due to receive a long suspension for his vitriolic outburst against UEFA following Wednesday's defeat against Barca.
There were some banners in the Estadio Bernabeu in support of Mourinho, who alleged that UEFA's referees systematically favour Barca, but possibly more revealing was the fact that around a third of the seats in the historic stadium were empty.
The Portuguese coach said afterwards: "This is my fault, obviously. Today I have not been capable of motivating my players sufficiently.
"In football, the difference in mental preparation is important, when one team is strong in terms of concentration and motivation but the other one isn't."
Mourinho raised eyebrows by leaving out Cristiano Ronaldo, which has been interpreted as punishment for the striker's criticizing Mourinho's ultra-defensive tactics on Wednesday.
Man-of-the-match Lafita gave Zaragoza the lead, against the run of play, just before half-time, after Real keeper Iker Casillas had made a real mess of a simple clearance.
Ten minutes into the second half Lafita was clumsily barged over in the box by the ageing Ricardo Carvalho, and Zaragoza captain Gabi calmly made it 2-0 from the resultant penalty.
Sergio Ramos gave Real hope by heading in a corner, but the impressive Lafita restored Zaragoza's two-goal lead 12 minutes from time.
Karim Benzema pulled another goal back for the hosts, but they were then crippled by the sending-off of Carvalho, a decision which predictably infuriated Mourinho.
Zaragoza then had to endure a furious but imprecise white assault in a frenetic finale.
Sunday's late game was scheduled to bring together lowly Deportivo Coruna and sixth-placed Atletico Madrid.