Calvin Johnson retired after the 2015 season, and at the time the main reason cited was the beating his body had taken over the years -- that he simply didn't want to go through the physical punishment anymore. Apparently the emotional strain of playing for the Lions also wore on him.

That's what he said in a recent interview, anyway. "I was stuck in my contract with Detroit, and they told me, they would not release my contract, so I would have to come back to them. I didn't see the chance for them to win a Super Bowl at the time, and for the work I was putting in, it wasn't worth my time to keep on beating my head against the wall and not going anywhere."

It's a little bit shocking: a young superstar walking away from the NFL while still relatively healthy and playing at an elite level? Of course another example of this that leaps to mind also used to play for the Lions: Barry Sanders.

Assuming this story doesn't lead to Johnson considering a comeback, he retired as one of the very best to ever play the position. In terms of yards per game, for example, the only two players better than him in the history of the league (3-plus seasons) are current players, whose averages may well decline. One has just three years of work under his belt. We'll see if they keep their slight lead on Johnson.

RECEIVING YARDS PER GAME, ALL-TIME
PlayerYPGYears
Julio Jones, Atl.96.32011-2016
Odell Beckham, NYG95.92014-2016
Calvin Johnson, Det.86.12007-2015
A.J. Green, Cin.83.02011-2016
Antonio Brown, Pitt.82.92010-2016
Josh Gordon, Cle.78.72012-2014
Mike Evans, T.B.77.82014-2016
Torry Holt, 2TM77.41999-2009
Marvin Harrison, Ind.76.71996-2008
Demaryius Thomas, Den.76.32010-2016
Jerry Rice, 3TM75.61985-2004
T.Y. Hilton, Ind.75.12012-2016
Lance Alworth, 2TM74.91962-1972
Michael Irvin, Dall.74.91988-1999
Andre Johnson, 3TM73.52003-2016
Terrell Owens, 5TM72.81996-2010
Sterling Sharpe, G.B.72.61988-1994
Brandon Marshall, 4TM72.22006-2016
Alshon Jeffery, Chi.72.22012-2016
Charley Hennigan, Hou.71.81960-1966
Larry Fitzgerald, Ariz.71.22004-2016
Randy Moss, 5TM70.11998-2012
DeAndre Hopkins, Hou.70.12013-2016
Amari Cooper, Oak.69.52015-2016
DeSean Jackson, 2TM69.42008-2016
Rob Gronkowski, N.E.69.32010-2016
Jimmy Smith, 2TM69.01992-2005
Don Hutson, G.B.68.91935-1945
Keenan Allen, S.D.68.92013-2016
Art Powell, 5TM68.81959-1968

--Andy Richardson