The Calvin Johnson/Julio Jones comparison

Detroit’s Calvin Johnson reportedly contemplates a farewell to the NFL at the tender age of 30. (Sean Gardner/Getty Images)Julio Jones turns 27 Wednesday.

Happy birthday to him.

And a sobering reminder to Falcons fans: The clock never stops ticking; the window never stops closing.

We were reminded once more of those immutable laws of time and physiology this weekend with the reports that former Georgia Tech receiver and current Detroit Lion Calvin Johnson was prepared to retire. At the age of 30. Just three years north of Julio Jones.

The talk was that Johnson had grown weary of playing with achy knees and ankles, and would turn his back on the nearly $68 million still owed him on a Lions…