Once again, there's no doubt that Cáceres is to blame for the goal. Anyone stating otherwise has never set a foot on a football pitch as a defender.
Either Martin needs to communicate to Ogbonna that he should push up (for an offside) or drop down (so that he can clear the ball). Cáceres does neither, marks Gomez himself and then drops him just before he receives the ball.
Martin chooses the lazy option. You can often get away with that, but not always. Been there, done that.
Say Ogbonna plays closer to Gomez (like some believe he should) and Ilicic passes the ball short to Borja Valero instead. Borja would have tons of space in front of the box and Ogbonna would be out of position.