Redskins quarterback Robert Griffin III said he will not keep playing the next time he sustains an injury.The statement comes in an ESPN The Magazine story released Wednesday. It is written as Griffin's letter to President Barack Obama "on behalf of a young man who recently moved to your district." Griffin first hurt his right knee Dec. 9 on a hit by the Ravens' Haloti Ngata. He stayed in the game briefly before leaving. He aggravated the injury during the first half of a playoff loss to Seattle. He remained in the game until the fourth quarter, when he tore multiple knee ligaments."Your survivor instinct kicks in," Griffin writes. "You're like, 'I'm a warrior. I'm a beast. I do all these things. I can push through adversity.' "But Griffin, who previously said he expects to be ready by the season opener, said he will not jeopardize his health again."If I had another incident like the Ngata hit, I'm out of the game," he writes. "You pull yourself out at that point. You learn from your mistakes."I don't feel like playing against the Seahawks was a mistake. But I see the mistake in it. With what happened and how everything was running, you take me out. If that happened again next year, I'd come out of the game and sit until I was 100 percent healthy." Tampa star dealt: The Chiefs traded cornerback and former Robinson High star Javier Arenas to the Cardinals for fullback Anthony Sherman. A second-round pick from Alabama in 2010, Arenas started a career-high nine games in 2012 with 59 tackles and a forced fumble. In 2011, he was third in the NFL in punt returns with a 12.8-yard average. Sherman was primarily a blocking back for Arizona. Corner done: Cornerback Al Harris retired. Harris, 38, played seven of his 14 seasons with the Packers and was a Pro Bowl pick in 2007 and 2008. He was out of the league in 2012. Gator signs: Ex-Florida receiver Frankie Hammond, who was not drafted, signed with the Chiefs. Bears: The league's first draft picks signed. Louisiana Tech offensive tackle Jordan Mills, a fifth-rounder, and Georgia defensive end Cornelius Washington, a sixth-rounder, received four-year deals. Financial terms weren't disclosed. Titans: Receiver Lavelle Hawkins will be released, the Nashville Tennessean reported. He had 47 catches in 2011 but only a combined 24 in his other four seasons, including five in seven games last season. UFL lawsuit: Players from the Omaha Nighthawks and Las Vegas Locomotives have sued the United Football League, 78 of them saying they haven't received any of the pay agreed upon in their contracts or in signed "personal guarantees" William Hambrecht, founder and chairman of the now-defunct league, filed a motion seeking the lawsuit's dismissal. His lawyer, Kristen Gallagher, wrote in court papers that player contracts require pay disputes to be arbitrated by the league's Football Advisory Committee, not the courts. But the players' lawyer, Andrew Rempfer, said no such committee exists and called the motion "flimsy." A hearing is set for next month.