Lopez trusts Martinez a lot and that's why he plays a lot.
but in terms of technical ability and talent or in general overall ability/potential he's pretty much the weakest CB we have. I'm guessing Gerard is using him because of his experience as Bueno and Cuenca are still young and not as experienced as he is.
But as time goes on I do expect those two at some point to overtake him once they gain more experience.
Always important to start the season with a win, especially away. It would be ideal if we'd have a strong first half of the season and then Gerard could give a chance to more youngsters when they will fully adapt.