NFL players past and present are reacting to Chris Borland's decision to retire from the San Francisco 49ers. The 24-year-old linebacker stepped away from the game after just one NFL season for fear of long-term head trauma.

St. Louis Rams defensive end Chris Long tweeted, "WOW. I loved Chris Borland's game but I can't fault him for calling it quits. His concerns are real. Still it takes a man to do the logical."

Former player Damien Woody tweeted that football will evolve but never go away because it's an avenue for so many guys to climb the ladder out of their situations.

Denver Broncos linebacker Brandon Marshall simply asked on Twitter, "So P. Willis and Chris Borland? They know something that we don't?" That was in reference to 49ers linebacker Patrick Willis, who also retired last week at age 30.

Borland tells ESPN's "Outside The Lines" he feels fine, but the long-term consequences of concussions aren't worth the risk.  (Metro Networks Inc)

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