Brian Dawkins says his head told him to retire, not his neck.

The veteran safety called Denver Broncos coach John Fox on Monday morning to tell him that after plenty of prayer and reflection, he'd decided that 16 seasons in the NFL was enough.

Then, Dawkins announced his retirement on Twitter, where he quickly began trending as fans worldwide expressed their admiration for the mild-mannered family man who transformed himself into a ferocious football player on Sundays.

Well-known by his alter-ego "Wolverine," and for his passionate, energetic play for 13 years in Philadelphia and three in Denver, Dawkins was one of the greatest to ever play his position, and nobody played safety in the NFL longer than he did.

Dawkins, 38, said he felt he had another year left in him after recovering from a serious neck injury that sidelined him for the stretch run and playoffs last season. But he instead fulfilled one final wish from his NFL bucket list: walking away from the game he loves before being betrayed by a battered body or one too many trips around the sun.

"It's probably going to sound crazy, but you know the fact that I could play another year gave me a lot of peace to say that this is it," Dawkins said.

Broncos boss John Elway said he wanted Dawkins to play in 2012 but never pressured him to return.

"It's always tough to take that final step," Elway said. "He'll be missed. He did so many tremendous things for the Broncos, not only on the field, but his leadership off the field was something that we'll always be grateful for."

Dawkins said the offseason additions of quarterback Peyton Manning and defensive coordinator Jack Del Rio forced him to pray a little longer on his future.

He insisted his neck didn't enter the equation, though. He said the nerve had regenerated and he was fine.

"My body feels good. It really does. My neck, that nerve area is cool, nothing's wrong with it," he said. "My strength is back where it was and my knees, things don't ache like they do during the season when I'm walking up and down the steps."

Dawkins said he felt great peace over his decision.

Dawkins said he wasn't sure whether he'd sign a one-day deal with his old team to ceremoniously retire from the team that drafted him in the second round out of Clemson in 1996, but one thing's for sure: he's staying in Denver, where he hopes to help coach high school football in the fall.

"I'll raise my kids here," he said. "This is a beautiful spot."

He also has a soft spot in his heart for Philly, where he plans to meet with the media on Saturday.

For 13 years, he was the heart and soul of the Eagles' defense.

"The NFL will miss a player as talented, ferocious, and determined as Brian Dawkins," Eagles coach Andy Reid said. "He was one of the most dedicated and hardest working players I have ever coached. Whether it was on the practice field, the film room or the weight room, Brian always put in the extra hours it took to become the star player that he was. And he transferred all of that and more onto the field on Sundays."

Dawkins finished his career in Philadelphia in 2008 as the franchise's leader in games played (183) and interceptions (34) while spearheading a defense that made the Eagles perennial championship contenders.

"Brian Dawkins is one of my all-time favorite players and one of the best to ever put on an Eagles uniform," team owner Jeffrey Lurie said. "On the field, in many ways, Brian re-invented the safety position. He had the speed and athleticism to line up against the game's best receivers, and was equally effective in the run game. His love for the game was infectious and he poured his entire heart and soul into everything he was doing from the moment he entered the stadium until he left.

"Everyone who ever watched Brian play saw that and it was impossible not to love that about him."

The Eagles announced they would honor Dawkins at their Sept. 30 game against the New York Giants, and the Broncos have plans to do the same at a later date.

Longevity isn't normally associated with the position where the hardest hits are both received and delivered — the only other safeties to log 16 seasons in the pros were Hall of Famer Paul Krause and Eugene Robinson.

Dawkins was named to several All-Pro teams and the NFL's All-Decade team of the 2000s and he made nine Pro Bowls, including last season as an alternate. Dawkins finished his career with 17 fumble recoveries, 26 sacks, 37 interceptions, 42 forced fumbles and 98 pass breakups. His 42 forced fumbles are the most ever by a defensive back in the NFL.

"Brian Dawkins is one of the best to ever play the game, a future Hall of Famer who changed the way his position is played," Fox said. "In many ways, he helped my job as a coach with his great leadership and preparation. He brought so much to the table and was such an enormous asset to our football team."

As a member of the NFLPA executive committee, Dawkins pushed for new league rules that limited full contact during camp and also in the regular season. He credited those changes in the 10-year labor pact reached last summer with keeping him fresh at the beginning of what turned out to be his final season, which he played a year after laboring through sprains to both knees.

What he was really fighting for, he said, was the next generation of players who will one day walk away from the game in better shape than he could.

It was one last piece of his long legacy.

"I just hope that people will remember me as someone that went out and gave everything that he could every week," Dawkins said. "Not just the weekend or the day of the game, but every week ... and that my teammates could count on me to be there all of the time. Not some of the times, not most of the times."

One tweet in response to Dawkins' retirement announcement came from Elway himself, who wrote, "Congratulations on a Hall of Fame career, Dawk!!!"

He'll be eligible for enshrinement in 2017.

"If that's something that happens, that will be a blessing," Dawkins said. "I never entered into the NFL saying that, you know, I'm going to be a Hall of Famer. I know some guys do that; I just wasn't one of them. I mean, that wasn't my mindset. I did not enter the league saying I want to play 16 years. None of these things were in my mind."


Follow AP Pro Football Writer Arnie Stapleton on Twitter: http://twitter.com/arniestapleton