MIAMI — Former NFL tackle Jonathan Martin posted on Facebook that difficulties in the profession led him to attempt suicide multiple times, and he wanted to share his struggle with social isolation to help others.

Martin, who retired this year, said his problems date to his childhood in California, and to being told his entire life he was not “black enough.”

“It nearly destroys you, many times, not fitting in,” he wrote, referring to himself in the third person. “Your talent & accomplishments on the field never seem to be able to overcome the demons that you carry with you.”

Martin made national headlines when he abruptly left the Miami Dolphins during the 2013 season amid reports he was bullied by teammates on the offensive line, including Richie Incognito. Martin underwent counseling, Incognito was suspended and neither played for the Dolphins again. Incognito is now with the Buffalo Bills.

An NFL investigation determined Incognito and two other offensive linemen engaged in a pattern of harassment toward Martin.

In his post Wednesday, Martin referred to the Dolphins’ locker room situation with a profane synonym for “lousy.” Trying to fit in, Martin said, he abused alcohol, used marijuana and created a persona.

Martin played in 2014 for the 49ers. He signed this year with the Panthers but hurt his back during offseason workouts.

49ERS: A Santa Clara County grand jury indicted former San Francisco defensive lineman Ray McDonald on one count of rape of an intoxicated person.

The indictment stems from an incident last Dec. 15 at McDonald’s home.

Current 49ers linebacker Ahmad Brooks has also been charged by the Santa Clara County District Attorney’s Office with misdemeanor sexual battery for an alleged assault the same day involving the same victim.

BROWNS: Johnny Manziel’s right elbow soreness isn’t going away, so the team is shutting him down.

Coach Mike Pettine said Manziel will likely sit out Saturday’s exhibition at Tampa Bay.

FALCONS: QB Rex Grossman signed a one-year deal with Atlanta.

Grossman, who hasn’t thrown a pass in an NFL game since 2011, is trying to beat out T.J. Yates and Sean Renfree for the primary reserve role behind three-time Pro Bowl selection Matt Ryan.

WASHINGTON: Linebacker Junior Galette injured his left ankle in the final minutes of practice.

Coach Jay Gruden said there was a “big chance” that Galette would not play in Saturday’s preseason game against the Ravens.

BRONCOS: Denver released kicker Connor Barth to make room for Pro Bowl left guard Evan Mathis.

GIANTS: Two-time Pro Bowl defensive end Osi Umenyiora is retiring as a member of the Giants.

Umenyiora, who won two Super Bowls with the Giants, signed a one-day contract and announced his retirement after 12 NFL seasons, the first 10 with New York and last two in Atlanta.

Umenyiora had 75 of his 85 sacks with the Giants.