Athletic Bilbao's impressive 3-2 win over Manchester United at Old Trafford in the Europa League on Thursday has given the Basque side a huge confidence boost.
Marcelo Bielsa's team, who are fifth in La Liga one point outside the top four, head to play local rivals Osasuna (seventh) on Sunday.
"It's one of those games you will always remember," Bilbao and Spain striker Fernando Llorente told reporters in Manchester.
"We played them without fear, and penned them back. We deserved to have scored more but we leave here very pleased."
Second-placed Barcelona trail leaders Real Madrid by 10 points with 13 matches left and travel to Racing Santander on Sunday without the suspended Gerard Pique.
The Spain defender was sent off last weekend and an appeal was rejected during the week. He is also being investigated for accusing the referee of appearing to make a "pre-meditated decision" when he showed him a straight red card.
Coach Pep Guardiola is without the injured David Villa, Alexis Sanchez and Ibrahim Afellay while Thiago Alcantara, Eric Abidal and Carles Puyol are all doubts.
Real are seeking their tenth consecutive away win when they visit Real Betis on Saturday and have a doubt over striker Karim Benzema.
The France international has been out of action since he picked up an injury against CSKA Moscow in the Champions League last month.
Third-placed Valencia host Real Mallorca on Sunday with striker Roberto Soldado boosted after ending a 49-day goal drought for his club. He scored twice in their 4-2 home win over PSV Eindhoven in the Europa League on Thursday.
Soldado returned to the Spain squad for the first time since 2007 and scored a hat-trick in their recent 5-0 demolition of Venezuela. He is fighting to be included in their Euro 2012 squad.
Fourth-placed Levante go to sixth-placed Malaga on Saturday. The home side will be without former Arsenal forward Julio Baptista, who has suffered yet another injury setback.
The Brazil international was close to a return after foot surgery but now has a calf problem and will return to Brazil to complete his recovery. In 14 months at the club he has managed only 15 league games but has scored 10 goals.
Atletico Madrid took a 3-1 lead over Besiktas in the Europa League on Thursday, Argentine Eduardo Salvio scoring twice as they shrugged off the absences of the injured Diego Ribas, Arda Turan and Tiago.
"He has worked hard to make this happen, he is a great alternative for the team," Atletico coach Diego Simeone said. The ninth-placed side host Granada on Sunday looking to end a run of five league games without a win.
