Theres a difference between breaking down in the middle of a game and crying at after you lose an important match, messi cried after argentina were knocked out. Casillas cried after iniesta scored in the world cup final. Marc has never broken down in the middle of a game and has always showed heart and determination, showed more leadership than anyone on the field yesterday.
Leadership isn't just about conduct in-game. When a team tastes defeat, it looks to the leader to derive strength, and restore the morale for the road ahead. Marc is a softie. And I've never considered messi as captain material, and the casillas example is not the same.