Ronald Koeman criticised his Barcelona players for missing two penalties on Thursday as they needed extra time to end the cup run of third-division side Cornella and reach the Copa del Rey last 16.

Goals from Ousmane Dembele and Martin Braithwaite in extra time sealed a 2-0 victory for Barca but only after Miralem Pjanic and Dembele had both failed to score penalties in normal time.

Pjanic and Dembele join a list of five Barcelona players to have missed penalties this season, along with Lionel Messi, Antoine Griezmann and Braithwaite.

"I don't understand because normally there are enough players who can score penalties," said Barca coach Koeman. "Maybe they are scary, I don't know. Several players have failed and, above all, if you score one of the two penalties, you calm down.

"You cannot miss two penalties as Barca players. It's not serious."

Barca were looking for a reaction on the back of their shock loss to Athletic Bilbao in the Spanish Super Cup final on Sunday, when Messi was sent off for the club for the first time.

With Messi suspended, a rotated line-up laboured to victory after a third consecutive extra-time in eight days.

Pjanic missed the first penalty in the 39th minute after Ronald Araujo went down under a high foot from Albert Estelles, Cornella goalkeeper Ramon Juan diving low to his right.

Griezmann and Braithwaite both failed to finish early in the second half and then Griezmann blazed over on the volley after a clever free-kick from Pjanic.

Another penalty presented a golden opportunity in the 80th minute after another Estelles error, this time a handball. Dembele stepped up but the result was the same, his driven effort down the middle again kept out by Ramon Juan.

Cornella, who beat Atletico Madrid in the previous round, saw their resistance last only two minutes into extra time as the power of Dembele's shot from distance was too much for the keeper, who could only divert the ball in off the crossbar.

Estelles completed his nightmare night by being sent off before Braithwaite added a second on the counter-attack.