Just watched the game and there is enough blame to go around. Several times the defense lost contain at the point of attack and it allowed the Dirty Birds to break a long one. That's a combination of poor coaching and youthfulness.
I won't try to defend BVG and his defensive schemes but more times than not, players were close in position to make the plays. A couple of things stuck out. One was simply poor execution on basic tackling. Haven't seen so many whiffs and arm tackling attempts in my life. Secondly, and it directly relates to the first one... the Irish do not have the athletes yet to consistently get to the point of contact, engage the offensive player, and drive them back. So many times, I see the Irish defender a half a step late and then try to make an arm tackle.