Nelson Valdez scored in each half as promoted Hercules stunned Spanish champion Barcelona 2-0 at the Camp Nou, while Jose Mourinho won his home coaching debut in Real Madrid's 1-0 victory over Osasuna on Saturday.
Paraguay striker Valdez beat Victor Valdes in the 27th minute. He latched on to Tiago Filipe's centering pass from a swift counterattack to beat the goalkeeper in the 59th for his second goal, sealing Barcelona's first league defeat at home since May 2009.
While Barcelona controlled the play, Bojan Krkic, David Villa and Gerard Pique all missed first-half opportunities.
"We didn't come here just to show up," said Valdez, who joined from Borussia Dortmund in August. "We took advantage of our opportunities and we knew that's what we had to do."
Madrid, meanwhile, rebounded from an opening draw at Mallorca with a convincing win at the Santiago Bernabeu stadium.
Ricardo Carvalho shot into an open goal in the 48th minute after receiving from Cristiano Ronaldo.
Osasuna 'keeper Ricardo Lopez made a number of goal-saving stops on Gonzalo Higuain and Ronaldo throughout, including a point-blank chance that fell back to the Portugal forward to feed poaching defender Carvalho for the winner.
"It was an easy game, we didn't have any problems and (goalkeeper Iker) Casillas didn't face one difficult situation," Mourinho said. "We easily controlled the game, without problem."
Atletico Madrid and Valencia maintained their perfect records after both made it two straight wins to start the season.
Diego Forlan capped an impressive Atletico buildup with his league-leading third goal in the 11th minute before Tiago headed home with 10 minutes remaining to secure a 2-1 victory at Athletic Bilbao.
Striker Sergio Aguero moved through three Athletic defenders along the left side before centering to Sabrosa Simao, who smartly laid off for Forlan to send a shot inside the far post.
Substitute Diego Costa led a counterattack that saw Simao's tough shot stopped but Tiago well placed to score from the rebound before Fernando Llorente redirected one back for the hosts in the 88th.
Valencia joined Atletico on six points but below on goal difference with a 1-0 win over Racing Santander, which dropped to 0-2. Madrid has four points and Barcelona three, same as Hercules.
Moments after Santander goalkeeper Antonio Rodriguez had saved from striker Aritz Aduritz in a one-on-one situation, Hedwiges Maduro headed past him in the 47th at the Mestalla stadium.
Hercules' last trip to the Camp Nou - during the 1996-97 season - was also victorious, winning 3-2.
"A complicated year awaits us," Barcelona coach Pep Guardiola said. "We'll need to pick ourselves up now."
On Saturday, Sergio Busquets did not play while Javier Mascherano started for the first time since his transfer to Barcelona from Liverpool. In all, eight Barcelona players who featured in Argentina's 4-1 midweek friendly win over World Cup champion Spain featured.
Former France striker David Trezeguet was also in Hercules' starting 11 after joining from Juventus.
Barcelona began well with Lionel Messi having a weak shot saved before Bojan poked Maxwell's centering pass wide in the ninth minute after an exquisite through ball by Villa.
Messi would have few decent touches after that, and Valdez soon silenced the home supporters after jumping on the rebound left by Valdes, who saved Abraham Paz's initial shot from inside the box.
Villa nearly equalized with a left-footed shot in the 33rd minute before Pique headed wide from close range. Guardiola made changes after the restart with Xavi Hernandez replacing the ineffective Mascherano and Pedro Rodriguez on for Bojan but Villa's chance in the 71st was as close as the Catalans would come to scoring after Valdez made it 2-0 with a hard shot over the outstretched Valdes.
"We lacked fluidity tonight," Guardiola said. "They closed down the interior lanes very well and it's hard to attack a team that plays so well as a unit."
Despite a scoreless first half, Mourinho's team looked assured and controlled play from the 22nd when Lopez got down to tip Ronaldo's one-timer from a Mesut Oezil pass wide.
Carvalho, who is playing with Mourinho for a third different club, provided Madrid's offense with the cushion it needed to go forward securely. Although efforts came, Lopez was too strong as he stopped Higuain point-blank with a reflex save in the 64th before Oezil chipped over the Spanish goalkeeper but past the far post moments later.
Lopez was down again to get a hand to Higuain's low shot in the 82nd before keeping Ronaldo's hard drive from the left side out at the short side. Ronaldo showed no effects from an ankle injury.
"I'm sure (Ronaldo) and Higuain are feeling some anxiety to score but I'm not worried about that," Mourinho said.
Madrid's defense kept Osasuna from creating any dangerous chances, while Oezil showed his ability to control Madrid's rhythm impressively in front of 68,000.
"He played with personality," Mourinho said. "He makes quick decisions and that's an art."
