American Football Rules IFAF Approved Ruling 7-3-8:IX

IX. A88 and B2 are running closely together before or after the ball has been thrown. Either A88 or B2 or both fall when their feet become entangled. Neither player was tripped intentionally. RULING: No foul. [Cited by 7-3-8-b-2, 7-3-8-c-2]