One of the aspects of Aikido we are constantly exploring is that if an attacker or body does not perceive a threat (such as a strong grab or hard block) they will naturally not react defensively (or at all). Staying relaxed and soft can help the other person become relaxed and soft, too.
This football play is a great example of this idea in action. The guy with the ball doesn’t tuck his head and charge through the line, instead he walks through like he has no place special to be. It’s so soft, relaxed, and casual the whole opposing team fails to perceive the threat – until he starts to run, and then it’s too late. Freaking brilliant. (And legal, too.)