Xavi's future remains in doubt amid claims president Joan Laporta is considering replacing him.
After victory over Rayo Vallecano, Roberto said: "We were playing for second place, we couldn't relax.
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"He (Xavi) is friend. Of course, I've always said, Xavi has always been fundamental.
"The criticisms? Even if we try to distance ourselves from everything, it is impossible. Friends send you things, even at the stadium... but we players only have to focus on the pitch. The quieter things are, the better for the players.
"I think that in the two in midfield is where I feel most comfortable and can help the team."