Ferguson, the fourth overall pick in 2006, has no known injury issues. Not only did he play every game in 10 seasons -- 167 consecutive starts, including playoffs -- but he also never missed a practice and never appeared on an injury report.
In fact, Ferguson missed only one offensive snap in 10 years, and that was a trick play when the entire offensive line was removed.
Ferguson couldn't be reached for comment, but sources say he has decided to retire because he no longer feels he can play up to his usual standard. His performance slipped last season, fueling speculation about his future with the Jets.
With a $14.1 million cap charge for 2016, Ferguson was an obvious candidate for a pay cut. The Jets have less than $1 million in cap room and still hope to re-sign quarterback Ryan Fitzpatrick.
Ferguson was approached last week in the weight room by general manager Mike Maccagnan, who broached the possibility of a pay cut. The conversation was brief. The Jets and Ferguson's agent never engaged in formal discussions about reworking his contract, sources said. By then, Ferguson already was considering retirement, according to sources.
His departure frees up $9 million in cap room.
Ferguson's decision has nothing to do with the proposed pay cut, sources said. He was confident he could have found a starting job elsewhere and has compiled $67 million in career earnings, so it wasn't about the money, the sources said.
"He just felt it was time," one source said.
The Jets aren't blindsided by the decision either. They have already been working toward securing his replacement. The free-agent market for offensive tackles is thin, but they could make a trade or draft a left tackle in the first round with the 20th pick.
The biggest name on the trading block is the Denver Broncos' Ryan Clady, a former Pro Bowl player who missed last season with an ACL tear. Taylor Decker, Jason Spriggs and Germain Ifedi could be options at No. 20 in the draft.
Even though he never suffered an injury, Ferguson has expressed concern about his well-being after football. He made headlines in December when he spoke candidly about the leaguewide concussion issue, acknowledging it could affect how long he plays.
After seeing the movie "Concussion," Ferguson wrote a piece for SI.com, saying he felt "betrayed" by NFL medical personnel who tried to downplay the long-term effects of concussions.
Referring to the premature retirement of former San Francisco 49ers linebacker Chris Borland, Ferguson wrote: "I thought perhaps he was acting very abruptly, but I now cannot fault him. If we know the risks, then why do we still play?"
Ferguson was a Pro Bowl selection from 2009 to 2011, when he was known as one of the best pass-protecting left tackles in the league. He recently received a lukewarm assessment from Jets coach Todd Bowles, who worked with Ferguson for the first time last year.
"He did some good things, and he did some not-so-good things," Bowles said at the owners meetings in March.
Asked if he expected Ferguson to play for the Jets in 2016, Bowles said, "Right now, he's on our team. We'll see how it goes."
Ferguson played more than 10,000 snaps in his career, missing only one -- the final play of the 2008 season. Then-coach Eric Mangini called a gadget play with skill-position players lining up as offensive linemen, with cornerback Darrelle Revis assuming Ferguson's left tackle spot.
"I count it as a blessing, and I don't take it for granted," Ferguson said last season, referring to his streak, adding, "I haven't had any major bang-ups. I mean, I've been banged up, but not to the point where I couldn't play. Stuff has happened, [but] nothing ever that bad."