When two guys get in each other's face up close in a stare down contest, peripheral vision goes out the window. Around the 5 second mark, watch how the attacker quickly dropped his left foot back before throwing a "blindside" hook punch.
This is why a man needs to control the distance and space between himself and the attacker for better peripheral vision awareness.
Note: "Peripheral vision awareness" is when one can see or detect an attacker's movement (from an arm length/mid-range distance) - i.e., clenched fist, jaw tightening, foot stepping forward or back, hand reaching into his pocket, etc.
Also demonstrates that weaknesses of character can make you vulnerable like the video above and open you to manipulation. i.e. being goaded into a trap.