Barcelona failed to get their title defence off to a winning start when they were held to a 0-0 draw at promoted Alaves on Saturday.
Argentine goalkeeper Roberto Bonano, released by Barcelona two years ago, produced a succession of top-class saves to earn Alaves a point on their return to the Spanish Primera Liga.
Barcelona laid siege to the Alaves area but last season's leading scorer Samuel Eto'o, winger Ludovic Giuly and World Player of the Year Ronaldinho were unable to find a way past Bonano.
"It was a good game against a well-organised team," Barca captain Carles Puyol told reporters.
"We tried everything we could but when 'Tito' [Bonano] didn't stop us we ended up being frustrated by the woodwork."
Valencia, Barca's predecessors as champions, made amends for their midweek defeat by Hamburg SV in the Intertoto Cup when Pablo Aimar secured a 1-0 win at home to Real Betis.
The Argentine playmaker curled in a right-foot shot after neat control on the fringe of the area eight minutes into the second half.
However, the honour of scoring the first goal of the new season fell to Athletic Bilbao midfielder Fran Yeste who grabbed his side's opener in the 47th minute of their 3-0 home victory over Basque rivals Real Sociedad.
Towering striker Fernando Llorente added the second four minutes later with a deflected shot.
Bilbao defender Luis Prieto wrapped up the points when he ghosted in at the far post to convert a free kick from Tiko.
Last season's runners-up Real Madrid begin their bid for a first title in three seasons by visiting promoted Cadiz on Sunday.
Returning to the top flight after two seasons in the second division, Alaves signalled their intentions from the start as they tried to muscle the visitors off the ball and play on the break.
But Barcelona gradually found their rhythm and settled into their customary fluid passing game after the first quarter of an hour.
Bonano produced reflex saves to deny Eto'o and Giuly before pulling off an acrobatic one-handed effort to turn a powerful drive from Deco round the post.
Coach Frank Rijkaard's side continued their siege of the Alaves area in the second half but again came up against Bonano.
The Argentine international parried a venomous drive from Ronaldinho and produced another spectacular diving save to stop his follow-up.
Four minutes later he got the faintest of touches to turn another fierce shot from the Brazilian on to the post and then stood up well to stop Eto'o cashing in on a poor back-pass.
Barca remained camped in the Alaves half but were unable to find a way past Bonano.
Eto'o lashed wide 17 minutes from time and drilled an angled shot against the base of the post in the next attack while Ronaldinho brushed the bar with two dipping free kicks.
Alaves almost snatched an unlikely victory when striker Rodolfo Bodipo smashed a close-range shot against the woodwork after a lightning counter-attack.