Why do my Dragon Rushes sometimes result in no damage?

When I use a Dragon Rush against an opponent, most of the time it executes an animation of my character pummeling the opponent and then knocking the opponent into the air, with the Rush itself doing some damage. However, sometimes when I use it and it connects with the opponent the animation changes to both characters throwing punches and the result is both of us disconnecting with no damage done.

What dictates whether the Dragon Rush is countered?