Ryan O'Callaghan, who played five seasons in the NFL for the New England Patriots and Kansas City Chiefs, and came out of the closet in June 2017, has released a tell-all book about his time in the professional football organization.

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I'm proud to announce my first book "My Life On The Line" is complete and available for pre-order from all major booksellers!! . After coming out publicly I was offered the opportunity to publish my story…so I took it! I saw this as a great way to reach those who need to read a story like mine and a fantastic opportunity to raise money for charity. 100 percent of my profits are going directly to The Ryan O'Callaghan Foundation (www.ROFDN.org) to benefit LGBTQ students, primarily athletes! . Please show your support and pre-order a copy today. *Release date is September 3, 2019* . @cydzeigler deserves special recognition because this would not have been possible without him! . #author #authorsofinstagram #nfl #football #akashicbooks #gay #lgbt #patriots #newenglandpatriots #instagay #charity #allforcharity #pleasebuythebook

A post shared by Ryan O'Callaghan (@ocallaghanryan) on Jul 8, 2019 at 11:55am PDT

Among the revelations in My Life On The Line: How the NFL Damn Near Killed Me and Ended Up Saving My Life, co-written with Outsports' Cyd Ziegler, is one about the number of closeted players in the league.

Said O'Callaghan to Thomson Reuters: “I can promise you there's plenty of closeted NFL players. I think it's safe to say there's at least one on every team who is either gay or bisexual. A lot of guys still see it as potentially having a negative impact on their career. … It's going to take a high profile player who's playing currently, coming out, to really make a difference.”

O'Callaghan also recalls the support he got from Patriots owner Robert Kraft and other players (Patriots Kevin Faulk, Andre Tippett, Dan Koppen and Deion Branch) after coming out. Kraft told him, “What you did took a lot of courage. I'm so proud of you.”

Wrote O'Callaghan in the book's epilogue: “Spending a few minutes privately with Mr. Kraft in his office is surreal. It's just him and me, with a couple hundred people outside his office door. …I never got that treatment when I was on his payroll. For (Kraft), who opens up to me about a gay friend, I am the most important person in the world in those few moments. Given where I have been in the previous dozen years, he is equally the most important person in the world for me right then and there.”