Lionel Messi scored what proved to be the winner as Barcelona beat Espanyol 2-0 to reach the Copa del Rey semifinals on Thursday in a game that saw Philippe Coutinho make his long-awaited debut.

Luis Suarez scored an early opener in the quarterfinal second leg before Messi's deflected effort gave Barcelona a 2-1 aggregate advantage as the holders overturned a 1-0 deficit from last week's first leg.

Messi had missed a penalty in that match as the leaders of La Liga were beaten for the first time since August, but they did enough on Thursday to join Sevilla, Valencia and Leganes in Friday's draw for the last four.

Coutinho was named on the bench for the first time since his 160 million-euro ($192 million) transfer from Liverpool earlier this month.

The 25-year-old Brazilian was introduced midway through the second half in place of Andres Iniesta, entering the Camp Nou pitch to a huge roar from the home crowd.

By that point Ernesto Valverde's men had already turned the tie around against the club for whom Coutinho played on loan from Inter Milan in 2012.

"We are placing a lot of hope in Coutinho," said Valverde.

"He is going to do well for us in the game. He can help us because he knows how to create, he's good in the one-on-one situations.

"He is also a player who's able to see the free man. We know he can be a danger with a shot or a decisive pass. I think he made a good start."

Suarez headed in Aleix Vidal's cross from the right at the back post in the ninth minute to open the scoring on the night and level the tie on aggregate.

The Uruguayan has now scored seven times in Barcelona's last six matches.

Messi scored in the 25th minute, his shot beating goalkeeper Pau Lopez with the help of a sizeable deflection off Brazilian defender Naldo.

It was Barcelona's 4,000th goal at the Camp Nou in an official game.