Leaders Real Madrid and champions Barcelona, three points behind their great rivals in second, are both missing key players for Saturday's games in the Spanish capital against Atletico Madrid and Getafe respectively.
Real's Brazil playmaker Kaka, Portugal centre-back Ricardo Carvalho and Spain full-back Alvaro Arbeloa have not recovered from injury and will miss the derby at the Bernabeu.
Barca playmaker Andres Iniesta, who sat out Wednesday's 3-2 Champions League win at AC Milan with a thigh problem, has not been included in the squad for the late kickoff at Getafe's Coliseum stadium.
Real coach Jose Mourinho marked Xabi Alonso's 30th birthday on Friday by underlining the importance of the Spain midfielder to the team.
"I don't want to say that he is irreplaceable because I don't want to go to such an extreme," the Portuguese said at a news conference.
"He is a man who provides balance," the former Inter Milan and Chelsea manager added. "He feels strong and often the biological age is not what's important."
Atletico, who have not beaten Real since 1999, are in ninth after an erratic start to their campaign under new coach Gregorio Manzano and Mourinho said Madrid's second club had no chance of winning the La Liga title.
"But with the squad they have they should be fighting for a Champions League qualification place and with more working time maybe in the future they can challenge for the title," he said.
"Great squads can be turned into great teams and tomorrow I expect a good team."
Atletico will be without their new striker Radamel Falcao on Saturday after the Colombian lost his fitness battle and was left out of Manzano's squad.
Falcao's absence means Spain Under-21 international Adrian will likely play up front, with Argentine forward Eduardo Salvio in support.
Manzano said Atletico would be looking to avoid the mistakes they made in September's 5-0 drubbing at Barca.
"Obviously we are going to play a more closed game, without the freedom of space that characterises our usual system and that led to defensive errors that we have to avoid tomorrow," he told a news conference.
"We do not want an open match because Madrid have tremendous counter-attacking ability."
Barca coach Pep Guardiola said the squad were missing his assistant Tito Vilanova, who underwent successful surgery on his saliva glands this week and will be laid low for about a month.
"We are noticing his absence in every sense of the word," Guardiola told a news conference on Friday. "He is a close friend of mine and at the same time we miss him a lot because he makes up for what I lack when I take charge of the team."
Third-placed Valencia, four points behind Barca after their 3-2 defeat at home to Real last weekend, also play in Madrid on Saturday, with a trip to
