The origins of the Sherman-Crabtree feud go back to an off-field incident this past spring in which Crabtree and Sherman came to close to fighting. That is, they came close to fighting at a charity event.
This version of events comes from Richard Sherman's brother Branton, so it's obviously going to be skewed a little bit sympathetically toward the self-described "best corner in the game" Richard Sherman. But there is clearly something personal going with these two divisional foes, and this is the best explanation we have yet.
In a post-game piece on the Seahawks NFC Championship win, the Seattle Times explains why Richard Sherman and Michael Crabtree have beef. "Sherman has been upset with Crabtree since last summer, Explains the Times' Jerry Brewer. "Both attended Arizona star receiver Larry Fitzgerald’s charity event. While there, Sherman went to shake Crabtree’s hand, and Crabtree tried to start a fight, according to Sherman’s older brother, Branton."
"'I’m going to make a play and embarrass him,' Richard Sherman vowed that day," according to Times' account."In the article Richard Sherman wrote explaining himself published today on SI.com, Sherman simply says, "It goes back to something he said to me this offseason in Arizona, but you’d have to ask him about that."
From what I can tell, this charity event would have been the Larry Fitzgerald Double Play Celebrity Softball Game, actually played in April of 2013. A fundraiser for Fitzgerald's First Down Fund, the game advertised Sherman as a celebrity participant. Crabtree posted a Facebook photo from the event (scroll down to April 29, 2013) with the message, "Had a great time at Larry Fitzgerald's celeb softball game in phx."
So both were in attendance. But I cannot find any reports of incidents from that game, and reading between the lines of the above quotes indicates that little or no physical altercation took place.
Now it should be pointed out that Richard Sherman has frequently used the old "I was just trying to say 'nice game' to him" excuse in when involved in taunting incidents. Sherman was just trying to say "nice game" when he butt-slapped Jim Harbaugh. Sherman was just trying to say "nice game" when he did a 'U MAD BRO?' on Tom Brady.
But when it comes to taunting and trash talking, Richard Sherman does indeed have a nice game.