The ' No. 1' receiver means the outside receiver. (RebelGrove) Receivers on the outside are always the 'No. 1' receiver, and every receiver inside of them sequentially goes up.

A great receiver is such a complicated combination of traits agility, body control, strength, quickness, soft hands, physical stamina, concentration, focus, toughness, pride, eye-hand coordination, vision, intelligence, the ability to conceptualize concepts.