Real Madrid's Spanish title defense lurched to a new low on Saturday, as Kaka was sent off in a 0-0 draw at bottom club Osasuna.
The result means Jose Mourinho's third-placed team could fall 18 points behind Barcelona if the La Liga leaders win at Malaga on Sunday, while city rivals Atletico Madrid can move seven clear of Real by beating Zaragoza.
With top scorer Cristiano Ronaldo ending a run of 60 consecutive league appearances due to suspension, Real looked woefully short of attacking ideas despite the return of striker Gonzalo Higuain.
Kaka came on for winger Angel Di Maria just before an hour was played, but the 2007 world player of the year was booked twice within 18 minutes to leave his side a man short.
The Brazilian's first yellow card came for jumping with an arm raised and the second was for stopping the home players taking a quick free-kick, resulting in his first red for Real since signing from AC Milan for a reported $100 million in 2009.
Mourinho also brought on striker Karim Benzema and Mesut Ozil for Higuain and Luka Modric, but Real's best chance was ruled out for offside.
Los Blancos have now won only six of the last 12 matches in all competitions, and Mourinho's future at the nine-time European titleholders may hinge on next month's Champions League last-16 clash with Ronaldo's former club Manchester United.
His team have already lost seven times this season -- two more defeats than the whole of the 2011-12 campaign -- and all of them have been away from home.
"I liked the team's attitude, I have no criticism. Lots of players had great matches, like Albiol and Coentrao, who haven't played for a while and they performed very well in a very demanding match," said Mourinho, who was also without suspended defender Sergio Ramos.
"I never talk about the missing players. We have had players injured for a month or two and I've never talked about them. We also have players suspended and I have not used that as an excuse."
However, he hinted that his players were struggling to deal with the big points deficit they face in the title race.
"The explanation begins on the first match day and since then things have happened that I do not want to talk about," said Mourinho.
"After that, when the gap is big, one team plays without pressure and the other one feels like that they can't close the gap and there are motivational issues."
Iker Casillas retained his place in goal, having been handed a second chance alter an injury to his replacement Adan, but Mourinho would not guarantee that the Spain captain would stay in the team for Tuesday's Spanish Cup quarterfinal first leg against Valencia.
"He hardly touched the ball against Osasuna, but it can be said that in these two matches the team has been good defensively and he has been part of the team's defensive play. It is too early to say whether he will play against Valencia."
Valencia moved up to seventh in the table after beating Sevilla 2-0, with both goals coming from Spain striker Roberto Soldado.
Soldado netted twice from corners to take his tally to 11 in La Liga this season to put his team above Levante on goal difference, while Sevilla stayed 12th.
Earlier, Espanyol moved out of the bottom three with a 1-0 win at home to Celta Vigo, as Sergio Garcia scored a first-half winner.
Real Mallorca stayed just above the bottom three after a 3-1 defeat at mid-table Valladolid, whose German winger Patrick Ebert celebrated his return from injury with two goals.
In Italy, Inter Milan moved up to third place with a 2-0 win at home to lowly Pescara.
Argentine forward Rodrigo Palacio scored in the first half and then set up Colombian Freddy Guarin nine minutes after halftime to leave Inter six points behind leaders Juventus, who host mid-table Atalanta on Sunday.
Bologna moved five points clear of the relegation zone with a 4-0 win at home to Chievo, as former Italy striker Alberto Gilardino scored twice.