Monroe made his retirement official with an open letter on the Players' Tribune. In it, he singled out his long-term health as the primary reason for stepping away from the game:
I'm only 29 and I still have the physical ability to play at a very high level, so I know that my decision to retire may be puzzling to some. But I am thinking of my family first right now — and my health and my future.
The last 18 years have been full of traumatic injuries to both my head and my body. I'm not complaining, just stating a fact. Has the damage to my brain already been done? Do I have CTE? I hope I don't, but over 90% of the brains of former NFL players that have been examined showed signs of the disease. I am terrified.
The 29-year-old lineman spent the 2015 season with the Baltimore Ravens, but they released him after they selected tackle Ronnie Stanley in the first round of the 2016 NFL draft. Mike Freeman of Bleacher Report reported that an NFL general manager told him there were five or six teams interested in Monroe "at bare minimum."
Monroe is a vocal supporter of NFL players using medical marijuana to treat pain, which is a cause he didn't believe the Ravens agreed with, according to Ken Belson of the New York Times: "I can't say for sure whether or not my stance on medical cannabis was the reason the Ravens released me. However, as I've said in the past, they have distanced themselves from me and made it clear that they do not support my advocacy."
Following his release, Monroe continued his outspokenness in favor of players using marijuana rather than painkillers to deal with the rigors of playing in the NFL, per ESPN.com:
Despite the current uncertainties, one thing is for sure: whatever happens in terms of my professional football career, I will never stop pushing for the League to accept medical cannabis as a viable option for pain management.
I will do everything I can to ensure the generations of NFL players after me won't have to resort to harmful and addictive opioids as their only option for pain management.
After getting selected with the No. 8 overall pick in the 2009 NFL draft by the Jacksonville Jaguars, Monroe appeared in 93 career NFL games, starting 90 of them.
He was traded from Jacksonville to Baltimore in 2013 and signed a five-year, $37.5 million deal to remain with the Ravens following that season.
The Virginia product played in only six games last season because of a shoulder injury and missed 15 contests over the past two seasons combined after sitting out a total of just four games in his first five NFL campaigns.
Monroe generated interest from multiple teams on the free-agent market, per Anderson, but with injuries continuing to mount, he officially ended his pursuit of another NFL job.
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