i don't fault him too much for this. he's inexperienced. it was messi carrying the ball at the three of them and even then, the pass was one that few could pull off at that speed. cavallo probably didn't think there was a threat of a pass and was more worried about whether messi was going to dribble around them.
that all being said, i think defensively, our guys could use some coaching. 1v1, 2v2 situations. what to do when someone is driving at the back line like that, etc. personally, I think risa should have controlled the back line more. told someone to pressure messi or commit a foul much sooner. You simply can't let someone drive at your back line all the way into your own box.
Defending is not difficult, but it does need to be taught and practiced so that it's reflexive and instinctual. At least when it comes to 1v1 and 2v2 defending. Our guys are generally pretty terrible at it. You have guys with their hands behind their back outside of the box. Or they go to "pressure" the ball carrier but give a solid 5 yards of space, which is useless. I don't think it would take long to teach the basics and commit some time each week to practice. It would yield tremendous benefits going forward though, in my opinion.