Dani Alves has fired up Barcelona for Saturday's trip to Real Sociedad by telling his team-mates games like these will decide the title.
The defending Primera Division champion go into its second game of the season on the back of a 5-0 win over Villarreal, but that result was bettered by Madrid's 6-0 thrashing of Real Zaragoza.
Sociedad also got their campaign off to a winning start with a 2-1 win over Sporting Gijon and Alves has urged caution ahead of the trip to Anoeta.
"Although in general people think that the league is decided in the games against the major rivals, I think it can be won or lost at grounds such as this Saturday," Alves told Barca's official website.
The Catalans have reason to be wary having lost there 2-1 towards the end of last season.
Summer signings Cesc Fabregas and Alexis Sanchez both scored in the win over Villarreal and Alves has been impressed by how quickly the Chile winger has settled at his new club.
"Cesc's adaptation is no surprise to us," he said. "He already knew how Barca operated, he'd been here a long time.
"Alexis is from another country and another league and it did surprise us a bit how well he's integrated into the team. He's a star and stars integrate into the squad quickly.
"Alexis is one of those players who has a lot of fun with his team-mates. He's very lively and spontaneous. We're all delighted with them both."
Madrid will look to keep hold of top spot when it hosts capital rivals Getafe on Saturday.
Jose Mourinho could hand a home league debut to forward Jose Callejon, the summer signing from Espanyol.
"We had a good start to the season," Callejon told the club's official website.
"We proved to be in good form in Zaragoza and we must keep this up. We can't afford to drop points against Getafe because it is harder each year to win La Liga.
"I have faith in myself and so does the club. I want to show people in every training session and every game why I was signed.
"Real Madrid have the best players in the world, but we'll all get playing time and we'll have to make good use of it."
Valencia hosts Atletico Madrid at the start of a tough run of games which will also see Los Che take on Barcelona and Sevilla before the end of the month.
And striker Roberto Soldado knows coming through that tricky opening still in touch with Madrid and Barca will be key.
"It isn't going to be easy to keep up with Barcelona and Real Madrid, but our main objective is improving from last season," he told the club website.
"Nobody in the dressing room is even letting the possibility of defeat on Saturday cross their mind."
Elsewhere on Saturday, Villarreal will look to bounce back from its humbling by Barca with an improved performance at home to Sevilla.
On Sunday, two sides who enjoyed opening-day wins, Real Betis and Real Mallorca, go head to head.
Racing Santander welcome Levante, Osasuna host Sporting Gijon, Rayo Vallecano take on Real Zaragoza and Athletic Bilbao travel to Espanyol.
On Monday, Malaga entertain Granada.
