Barca are preparing for a potentially key run of fixtures running up to the Christmas break.

The Catalans travel to San Mames boasting a one-point lead over Real at the top of the Primera Division standings and having enjoyed plenty of recent success over the Basque outfit.

Not only did Pep Guardiola's side do the double over Athletic in the league last season, but they also thrashed them 4-1 in the final of the Copa del Rey and 5-1 on aggregate in the Spanish Super Copa this summer.

A repeat of those triumphs would be most welcome this weekend, as it would set them up nicely for a series of huge matches in the coming weeks.

Next Tuesday, Barca host Inter Milan in the Champions League knowing anything other than a victory could create serious problems, then arch-rivals Real travel to the Nou Camp for 'El Clasico' at the weekend.

Also before the Christmas break, Barca face a testing visit to Deportivo La Coruna and a derby against Espanyol in La Liga, as well as a daunting winter trip to Dynamo Kiev in a match that could decide whether the holders continue in the Champions League.

On top of all that, Barca also have commitments in the Club World Cup in Abu Dhabi next month.

"It's vital to win at San Mames and gain more confidence. The team always feels strengthened after a victory. It's also important to keep the league leadership, not only for the visit of Real Madrid, but against any team," said goalkeeper Valdes, who does not believe Athletic will have an extra reason for wanting to turn Barca over because of last season's events.

"I don't think they'll want revenge. They'll want to pick up the three points because they are very important to them.

"San Mames is a very difficult ground where we have always found it difficult. I think it will be a close game and will be a good spectacle."

If Barca slip up against Athletic, then Madrid will take over at the top of the table if they beat Racing at home earlier on Saturday night.

Madrid again look set to be without Cristiano Ronaldo as the world's most expensive player continues his comeback from an ankle injury, but the Portugal international is close to fitness and could be ready in time for next week's games against FC Zurich and Barca.

Madrid have won only four of their nine competitive matches since Ronaldo has been sidelined - compared to previously winning all seven with the £80million man in the side - but despite that slump in form, and talk of crisis, the Spanish giants are actually enjoying one of their best-ever starts to the league season.

Never since three-point wins were introduced in 1995/96 season have Madrid been as successful in their opening 10 games as this term, when they have accrued 25 points, scored 26 goals and conceded just eight.

Manuel Pellegrini's side will be determined to improve that tally this weekend, although to do so they will need to overcome someone who knows plenty about Madrid - Miguel Angel Portugal.

Portugal was unveiled on Thursday as the new Racing coach, having spent much of the last two year's working as Madrid's technical secretary.

The two other Primera Division matches on Saturday night see third-placed Sevilla travel to Tenerife and struggling Atletico Madrid, whose coach Quique Sanchez Flores is suffering from swine flu, are at fifth-placed Depor.

The remaining games are on Sunday, when in-form Valencia travel to Osasuna, Villarreal play host Real Valladolid, Xerez face Sporting Gijon, Espanyol welcome Getafe, bottom club Malaga meet Real Zaragoza, and Almeria travel to Real Mallorca.