Sevilla and FC Barcelona need victories this weekend to break the logjam atop the Spanish league standings. The leading pair haven't won in 2007, allowing Real Madrid, Valencia, Athletic Madrid and Zaragoza to move closer as the season reaches its halfway stage.
Only seven points now separate the top six sides, making Spain the closest fought of Europe's top soccer leagues. Sevilla is first with 37 points from 18 games, two points more than Barcelona and Madrid, although Barcelona has played a game fewer.
Valencia has 33, Atletico has 32 and Zaragoza 30. Sevilla, which lost a perfect home record this season against lowly Mallorca last weekend, aims to stem a run of two league defeats when it visits 11th-place Villarreal on Saturday.
Sevilla midfielder Christian Poulsen denied his team is buckling under the pressure of heading the league.
"The leadership isn't weighing us down. This is the best league in the world and any team can beat you," Poulsen said. Only a victory will suffice for Barcelona, which has won only one of its last five games, when it hosts last-place Catalan neighbour Gimnastic Tarragona.
Coach Frank Rijkaard has expressed his relief that the defending champion's slump hadn't arrived later in the year. "The good news is we're still in the first half of the season," Rijkaard said. "We're faced with a lot of work so we can improve and be better physically."
With Samuel Eto'o still injured, Eidur Gudjohnsen is facing stiff competition from Javier Saviola for the team's striking role. The Argentine has scored six times in the last three games, including all Barcelona's goals in the 5-2 aggregate win over Alaves in the Copa del Rey.
Madrid's visit to Mallorca on Sunday has been overshadowed by president Ramon Calderon's disparaging comments about David Beckham and the rest of the team on Tuesday.
Before this latest trouble, Madrid had appeared heartened by its first win in three games last Sunday against Zaragoza. Two of its trio of recent signings, Gonzalo Higuain and Fernando Gago, gave promising displays, and boosted Madrid's hopes that its new-look team will end three years of disappointments.
Madrid will need to replace injured captain Raul Gonzalez, Brazilian left-backs Roberto Carlos and Marcelo, right-back Cicinho, and midfielders Emerson and Jose Maria "Guti" Gutierrez.
But there appears little chance that coach Fabio Capello will relent on his promise not to pick David Beckham again after his announcement of his move to MLS side Los Angeles Galaxy at the end of the season.
Brazil striker Ronaldo has also been declared surplus to requirements and has emerged as a transfer target for AC Milan.
Mallorca's victory at Sevilla ended a run of four straight defeats and moved the island team up to 15th place. Valencia will seek its sixth straight win on Saturday when it hosts lowly Real Sociedad, whose recent revival was halted last weekend with a 1-0 defeat at Racing Santander.
However, Valencia suffered a setback on Wednesday when it was knocked out of the Copa del Rey after a 4-2 defeat by visiting Getafe.
Sociedad could hand debuts to its three new signings - former Brazil winger Savio Bortolini, and two Argentines, striker German Herrera and central defender Victor Lopez.
Atletico's home game against Osasuna on Saturday will be the teams' third meeting in 10 days.
Atletico will seek to atone for Wednesday's Copa del Rey elimination by its rival, which cost it a place in the quarterfinals.
Zaragoza faces on Sunday a tough home game against seventh-place Recreativo Huelva, which has won its past two away games against Madrid and Espanyol.
Levante, which has only won twice in 14 league games and is struggling in 17th place, will be under new coach Abel Resino for its home game against Athletic Bilbao on Sunday.
Resino took charge after Jose Ramon Lopez Caro on Monday became the fifth Spanish league coach to lose his job this season. Also this weekend, it's: Getafe vs. Celta Vigo; Real Betis vs. Santander; and Deportivo La Coruna vs. Espanyol.