Carson Palmer of the Arizona Cardinals announced his retirement Tuesday in an open letter after 14 seasons with three teams. Carson Palmer retirement news The 38-year-old quarterback — the Cincinnati Bengals' first overall draft pick out of USC in 2003 — said he believed it was simply time for him to step away from football. "Over the years, I've had teammates who decided to hang it up and I would ask them how they knew when it was time to walk away," Palmer wrote. "The answer was almost always the same: You just know. For me, that time is now. Why? Quite simply, I just know." An open letter from Carson Palmer. Carson calls it a career » https://t.co/3tkaqIqQaD#CheersToCarson pic.twitter.com/9m8Qs5yWpQ — Arizona Cardinals (@AZCardinals) January 2, 2018 The Heisman Trophy winner's (2002) career basically ended Week 7 in London after he broke his left arm against the Los Angeles Rams. Blaine Gabbert (five games) and Drew Stanton (four) started at QB for the remainder of the season. Palmer went 38-21 during five years in Arizona, a run that included leading the Cardinals to a 13-3 record and a spot in the NFC Championship Game in 2015. That was the furthest the passer — who also played two seasons for the Oakland Raiders (2011-2012) — ever got in the postseason. He threw for a career-high 4,671 yards and 35 touchdowns that year. Palmer finished his career with 46,247 yards, 294 touchdowns and 187 interceptions, with a career completion percentage of 62.5. He's 11th in career completions, 12th in passing yards and touchdown passes, and 14th in attempts. Palmer threatened to retire from the Bengals in 2011 after requesting a trade that wasn't immediately granted. He sat out the first six games of the season before being sent to Oakland. The QB had two major knee injuries during his career, in 2006 and in 2014. This caused him to miss 42 games in total. Palmer will retire fourth in Cardinals history in passing yard and touchdowns. He owns the franchise records for passing yards and passing touchdowns in a season. Several names have already begun circulating as potential replacements for Palmer, and ESPN cites Oklahoma's Heisman Trophy winner Baker Mayfield as the most likely choice. Mayfield, 22, began his college career at Texas Tech but left to join the Sooners after just one year. In December, Mayfield led Oklahoma to its third straight Big 12 Championship after the Sooners beat TCU 41-17 in the title game. Oklahoma will face Georgia in the 2018 Rose Bowl, a national semifinal, on Monday (Jan. 8). Cardinals backups Stanton, Gabbert and Matt Barkley are all set to become unrestricted free agents when their contracts expire in March. Arizona has the 15th pick in the first round of the 2018 NFL Draft and six overall picks. Among the other potential quarterbacks the Cardinals could choose, per ESPN, are Louisville junior Lamar Jackson, the 2016 Heisman winner, Washington State senior Luke Falk, and Oklahoma State senior Mason Rudolph. ESPN also listed current NFL free agents like Sam Bradford, Jay Cutler and Case Keenum. HOUSTON, TX - AUGUST 28: Carson Palmer #3 of the Arizona Cardinals passes against the Houston Texans in the first quarter of a preseason NFL game at NRG Stadium on August 28, 2016 in Houston, Texas. (Photo by Joe Robbins/Getty Images)