Barcelona midfielder Xavi has branded under-fire boss Gerardo Martino "a natural leader".

Despite leading Barca into the knockout stages of the Champions League and to the top of the La Liga table, the Argentine has come under criticism for his tactics this season.

However, Xavi has insisted that the players are fully behind their manager, who replaced Tito Vilanova at the beginning of the campaign.

"Tata, like [Pep] Guardiola, is a natural leader. He is rigid, demanding, he talks very directly and his ideas are very clear. We are very relaxed inside the dressing-room. We believe in what we are doing," Xavi told Radio Catalunya.

"We know that these are two consecutive defeats, and that the level of demands is very high. The fans pressure us a lot to return to playing the same as we did before, and that is difficult. But from inside we are relaxed, we know we are doing things well.

"Barca are not playing on the counter-attack, but for a passer like me it is always nice to find spaces [to play more directly]. The style does not change, it is all compatible."

Barcelona face Celtic in the Champions League on Wednesday.