First-half goals from Luis Suarez and Lionel Messi carried Barca through to an 11th semifinal in 12 years, with Coutinho brought on as a second-half substitute for Andres Iniesta.

The club's record signing had been sidelined with a thigh injury since he joined from Liverpool for €160 million earlier this month, but was given the green light to return to action on Wednesday.

Valverde introduced him in the 68th minute to a rapturous ovation from the second-largest Camp Nou crowd of the season, who proceeded to cheer his every touch.

During his cameo, he looked immediately at home, settling into Barca's style and creating a great chance for Suarez to make it 3-0.

"Good players always adapt well," Valverde said in his news conference, when asked about Coutinho's encouraging debut.

"We have high hopes for him here at the club, in the sense that he will be good for our style of play. He's a confident lad who can help us because he's good in one-on-one situations, he can spot the free man. ... And when he gets close to the area, you can sense the danger.

"It wasn't an easy game, but I think he did well. But let's see, this is just the beginning..."

By the time Coutinho was brought into the action, Barca had already engineered a two-goal lead, turning around the tie after losing the first leg 1-0 at Cornella-El Prat last week.

However, a goal for Espanyol would have seen them progress via away goals, making for some nervy minutes as Barca attempted to see the game out.

"I liked the performance, above all the way we managed the final stages," Valverde added. "We turned the tie around in the first half, but we had to look for a third goal because one for Espanyol would have knocked us out.

"In the end, we've managed the game well. Leo [Messi] took responsibility, getting on the ball, holding it and making time [to] pass. You have to know how to play with this type of pressure and tension. And we did. Espanyol were in the tie until the last minute and we had to work really hard."

Barca go into Friday's draw with Sevilla, Valencia and Leganes, who came from behind to knock Real Madrid out at the Santiago Bernabeu on Wednesday.

"The cup is tough," Valverde said after keeping Barca's hopes for a fourth successive Copa del Rey and a record 30th triumph alive.

"You can't be sure of anything. With what happened yesterday [Madrid losing to Leganes] and the day before [Sevilla beating Atletico], you can see it's not easy to get through.

"I think the teams that are in the last four are there because they have really worked hard. In these games, you can't have a bad day because you will be punished. You will be knocked out of the competition."