
Elsewhere, Frenchman Richard Gasquet beat his compatriot Gilles Simon with a 6-4 6-4 victory score.
Djokovic was not at his best when he played against Mathieu, however, he had the advantage because the French player was only able to benefit from three out of seven break points.
The Serb star had said it was because he wasn’t used to his new tennis racquet that he was beaten by Gulbis.
Jo-Wilfried Tsonga, also from France, defeated Simone Bolelli from Italy with a 6-4 6-1 result.