Barcelona produced a stunning display in Gerardo Martino's first competitive match in charge as they hammered Levante 7-0 at the Camp Nou on Sunday, while Real Madrid left it late to give Carlo Ancelotti a winning start as they beat Real Betis 2-1.
Spanish champions Barcelona showed no signs of early season rust as they ripped the visitors apart with goals from Alexis Sanchez, Lionel Messi, Dani Alves, Pedro and Xavi giving them a 6-0 lead at half-time.
There was even more for the home fans to cheer after the break as Neymar made his competitive debut as a substitute and even after Martino had shown the visitors some mercy by withdrawing Messi with 20 minutes remaining, more woeful defending allowed Pedro to round off the scoring with his second of the game.
"I was anxious for the league to start to see where the team were and I have been left very calm," said Martino. "We put a lot of emphasis on pressing and we managed to sustain it for the majority of the match."
It took Barça barely two minutes to register their first goal of the campaign as Sanchez finished off a fine team move before Messi opened his account for the season with a side-footed finish from close range. Alves added the third on 23 minutes before further strikes from Pedro, Messi from the penalty spot and Xavi made it six before half-time.
The Catalans weren't quite as clinical after the break but the moment many inside the crowd had been waiting for arrived on 62 minutes as Neymar made his competitive bow in a Barça shirt in place of the impressive Sanchez.
The Brazilian's only moment of note was when he picked up an unnecessary yellow card, but Barça did manage one more goal before the end as Pedro side-footed home his second of the night.
Isco finds a late winner for Real
It was a far more complicated evening for Real, however, as they needed a headed winner from debutant Isco four minutes from time to take all three points against a spirited Betis.
"I am very happy, above all for the victory," Isco told Canal Plus afterwards. "It is the first goal that I have scored with my head.
"The truth is that Betis surprised us a bit but it is the first game of the league, we have to improve a lot but we have just started."
Jorge Molina gave the visitors the lead their bright opening deserved on 14 minutes as Cedric Mabwati burst past Sergio Ramos and laid the ball across the area for Molina to slot home. Betis could even have been two in front moments later as Joan Verdu fired wide with the goal at his mercy after more good work from Mabwati.
Slowly but surely Madrid started to find their feet though and they were level midway through the first-half when Karim Benzema swept home from Isco's pass. Betis were inches away from retaking the lead just after the half hour mark though as Nosa rose highest to meet Verdu's corner and thundered a header off the bar.
After the break it was Madrid's turn to feel hard done by as Cristiano Ronaldo came within inches of marking his 200th appearance for the club with a goal as his shot from the edge of the area came back off the bar.
The Portuguese then had a great chance to give his side the lead as he was played in by Mesut Ozil but his low drive was straight at Stephan Andersen. Nosa then had another fantastic opportunity to put Betis back in front as he headed over when completely unmarked just ten yards out.
And Betis were made to pay for their profligacy in front of goal as with the clock winding down Isco made a fine late run into the area to meet Marcelo's cross and plant a header high past Andersen.
Bright start for Atleti
Atletico Madrid, who face Barcelona on Wednesday in the first leg of the Spanish Super Cup, also began their campaign with a 3-1 victory away to Sevilla thanks to a double from Diego Costa.
The Brazilian - who signed a three-year extension to his contract last week - opened the scoring 10 minutes before half-time only for Diego Perotti's wonderful strike from 25 yards to level matters two minutes later.
However, Costa was to have the final word as he strode onto Koke's pass to finish low past Beto in the Sevilla goal 11 minutes from time before Cristian Rodriguez added a third in stoppage time.
Elsewhere, Grenada earned a hard-fought 2-1 win over Osasuna with first-half goals coming from Youssef El Arabi and Hassan Yebda before Francisco Punal pulled one back for Osasuna, though it wouldn't be enough as Granada held on for the three points.