Barca back to winning ways in Cup opener
Barcelona's forward Pedro Rodriguez scores during ae Spanish Copa del Rey match against Cartagena at the Cartagonova municipal stadium in Cartagena on December 6, 2013
With Barca in need of a response after two disappointing performances, coach Gerardo Martino named a strong side including Alexis Sanchez, Cesc Fabregas and Sergio Busquets.
However, Fernando fired the hosts into a shock lead after just 16 minutes when he got in behind the Barca defence before finishing across Jose Manuel Pinto into the far corner.
Pedro Rodriguez calmed the visitors' nerves eight minutes before the break with an equaliser and Fabregas completed the turnaround with a neat finish seven minutes later.
Barca should have put the tie to bed early in the second period as Sanchez and Fabregas passed up fine chances to extend their advantage.
Pedro did eventually finally make it 3-1 15 minutes from time when he finished expertly from Sanchez's pass.
And Cameroonian teenager Jean Marie Dongou rounded off the scoring in stoppage time with his first senior goal for the club on the rebound after Pedro had struck the post.