Oscar Melendo scored the only goal of a game of few chances after Lionel Messi had seen his second-half penalty brilliantly saved by Diego Lopez at Cornella-El Prat.

Ernesto Valverde's side had last tasted defeat in August, when they were beaten by Real Madrid in the Spanish Super Cup.

Barca travel to Real Betis in La Liga on Sunday but will then have the chance to exact revenge on Espanyol in the second leg of the quarterfinal tie, which takes place at Camp Nou next Thursday.

"If you could choose a day to lose, it might have been today," Pique told reporters after a hard-fought Catalan derby.

"Because in a week we can turn things around at Camp Nou. The penalty [miss] affected us too much. From there, the game went in a direction we didn't want and we complicated things.

"We will approach the second leg differently. From the first minute, we will press high, we will try to create a lot of chances and hopefully the home support drives us on."

Pique was subjected to insults from Espanyol supporters about his relationship with singer Shakira during the game, while Barca goalkeeper Jasper Cillessen was struck by an object from the crowd.

"It's not up to me to take action on these matters, but we hope the same things don't happen at Camp Nou," the defender added when asked about the incidents.

"We hope that the supporters don't insult the players and throw things at them. I ask the fans to be respectful. Respect should always come first."

Like Pique, midfielder Busquets played down the significance of the end of Barcelona's unbeaten run, which falls short of the club's record of 39 games without defeat (under Luis Enrique in 2015-16).

"We knew [a defeat] was going to arrive at some point," Busquets said. "We tried to keep the run going as long as possible, but it wasn't to be tonight. The good thing is we have the second leg to try and turn things around.

"Luckily, the return game is at home, too, and we will have to go all out for the win. I don't think [losing a game] will affect the team."

As well as Messi's missed penalty, Denis Suarez sent a great chance wide in the first half, but in general, Barca struggled to break down a well-organised Espanyol side.

However, despite the lack of clear-cut chances and the one-goal defeat, Ernesto Valverde wasn't too downbeat with the performance.

"I quite liked how my team played," the Barca coach said in his postgame news conference. "The attitude was good and the players wanted to overcome the difficulties presented to them.

"It was difficult to play on the pitch at times. [Espanyol] has a plan to sit back and to close down space in the middle ... It was tough but we had it under control.

"But we weren't efficient in the final third and then, after the missed penalty, the crowd reacted and came alive. There was a bit of tension and they took advantage of those circumstances, caught us out at the back and scored. We have to accept the result."

Valverde made a number of changes to his side for the game. Some were enforced, with Andres Iniesta and Ousmane Dembele joining a lengthy injury list this week, while others, such as Luis Suarez, were left on the bench.

Those that came in -- Denis, Lucas Digne, Carles Alena and Aleix Vidal -- struggled to have an impact, but Valverde defended his team selection.

"We played with the same players in Vigo [against Celta] and I am happy with them," the coach said.

"We have players injured, others with knocks and we have to try and pick the best team for each game considering all circumstances. We have a lot of games close together at the moment and there are a lot of players that have played a lot."