The Argentine was unhappy with the Cameroon international and felt he struggled with his range of passing as Barcelona beat Cartagena 4-1 on Friday nightBarcelona boss Gerardo Martino criticised the performance of Alex Song after his side beat Cartagena 4-1 in the Copa del Rey.
The hosts took a shock early lead but two goals from Pedro, a Cesc Fabregas strike and Jean Marie Dongou's debut goal ensured victory on Friday night.
But Martino was left frustrated by the showing of the former Arsenal man and felt his positional play was out of sorts.
"Playing as a holding midfielder is not the same as playing as half of a midfield pivot pair," he said.
"At times, he did well but other times he was turned inside out and he was having trouble finding a second, alternative option with his passing."
The result brought to an end a run of two straight defeats and Martino was satisfied after getting back to winning ways.
"We were obliged to win, bearing in mind our recent outings, and we did," the Argentine told reporters afterwards.
"Cartagena played a very intense game, they did a lot of running and their attitude was good during the opening 10 or 15 minutes. Later, when we had control of the ball, they had no energy left."
Barca's next clash is a home Champions League tie at Camp Nou against Celtic, in their final group stage fixture.