He made one blunder which cost us a goal, but it doesn't mean it was his only one mistake in that game. He was very shaky in first half and the most dangerous situations to score Real had because of him. But this is not the most important thing, because - as you mentioned above, we can shift the responsibility onto Conte as well. Maybe he wasn't ready and Conte put him in the lineup too quickly after that car accident?
But, the problem is that Caceres is prone to make blunders sometimes, just like Bonucci, but to a lesser extent. He is just not good enough to play as a starter RB for us, because offensively he is very limited too. He can cross nice, but he can't run with the ball like Lichtsteiner, he isn't aggresive enough in attack, he doesn't have any idea how to dribble. That's why he should not be our first pick for right back.