If Calvin Johnson, Jr. retires, it just adds to the impressiveness of Jerry Rice's longevity and excellence. Hell, we could even point to Anquan Boldin's longevity and excellence. It's a rough game!
Megatron has dealt with numerous injuries during his career, and it might be wearing him down. His potential retirement says that much more about the longer careers of some wide receivers, including the G.O.A.T.