Miami — Former NFL tackle Jonathan Martin posted on Facebook that difficulties in football led him to attempt suicide multiple times, and he wanted to share his struggle to help others.

Martin, who retired this year, said his problems date to 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. “Your talent and 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 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 with the Bills.

An NFL investigation found Incognito and two other 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.

“You see football as the only thing that you are good at, your only avenue to make the shy, depressed, weird kid from high school ‘cool,’ ” he wrote.

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

After three years in the NFL, he decided the risk of permanent injury wasn’t worth it.

Manziel shut down

Johnny Manziel entered the NFL with a flair for making sensational plays. And, as it turns out, an elbow problem.

Manziel’s right elbow soreness — a problem the Browns said has troubled the former Texas A&M quarterback since he was in high school — isn’t going away, so the team is shutting him down.

Mike Pettine said the second-year quarterback likely will sit out an exhibition Saturday at Tampa Bay, and that team officials will discuss signing another quarterback.

The injury clears the way for Josh McCown to be named the starter for the Week 1 opener against the Jets.

Extra points

Two-time Pro Bowl defensive end Osi Umenyiora signed a one-day contract, then retired as a member of the Giants after 12 NFL seasons.

... Quarterback Rex Grossman, 35, who hasn’t thrown a pass in an NFL game since 2011, has signed a one-year deal with the Falcons and will try to beat out T.J. Yates and Sean Renfree for the primary reserve role behind three-time Pro Bowl selection Matt Ryan.

... The Raiders signed free-agent safety Taylor Mays, who was released last week by the Lions, and waived linebacker Chase Williams. Mays is reunited with defensive coordinator Ken Norton Jr.

... The Broncos released kicker Connor Barth to make room for two-time Pro Bowl guard Evan Mathis, meaning Brandon McManus has regained his status as Denver’s kicker.

... Defensive end Jadeveon Clowney, the top pick in 2014 who had microfracture surgery on his right knee in December, is expected to play in the Texans’ opener against the Chiefs.