SEATTLE – Four-time All-Pro Seattle Seahawks lineman Walter Jones has retired after a 13-year career during which he became a cornerstone of the team and one of the players against whom other left tackles were measured.

The 36-year-old Jones made the announcement in a team news release Thursday. It had been expected for months. Jones hasn't played since Thanksgiving Day 2008 and has had two knee surgeries in that span.

What a great day to be a seahawk," Jones posted on his Twitter page Thursday afternoon.

Jones will be at a news conference Friday afternoon at team headquarters in Renton, Wash., to discuss his decision and his career.

The team is immediately retiring Jones' number 71 jersey. Former Seahawks coach Mike Holmgren has called Jones the best offensive player he ever coached, and Holmgren has coached Brett Favre, Joe Montana, Steve Young and Jerry Rice.

The Seahawks have only retired two other jerseys, No. 80 for Hall of Fame wide receiver Steve Largent and No. 12, for their "12th Man," the team's fans.

Walter Jones: One of the all-time greats to ever play the game. You will always be a part of the Seahawks!" new Seahawks coach Pete Carroll tweeted later.

Washington Gov. Chris Gregoire is declaring April 30 "Walter Jones Day.

Last week, Seattle drafted Russell Okung sixth overall and immediately said the rookie from Oklahoma State would be Jones' replacement for 2010. Okung will be the Seahawks' second regular left tackle in 14 years.

Okung remembers passing by Jones' locker at Qwest Field a couple of years ago while Oklahoma State was in the Seattle for a game there against Washington State.

My strength coach stopped me to look at it," Okung said. "And I thought, 'If I could ever be even as good as Walter Jones ...'

Seattle used a sixth overall pick in 1997 to select Jones out of Florida State.

He immediately showed he belonged and he became part of the foundation that Holmgren used to help steady a previously meandering franchise.

Within two seasons, the 6-foot-5, 325-pound Jones became Seattle's first offensive lineman to make a Pro Bowl. He ultimately earned eight more Pro Bowl selections, his last for the 2008 season.

Jones led an offensive line that helped Shaun Alexander to what was then the fourth-best rushing game in NFL history, 266 yards against Oakland on Nov. 11, 2001.

On Sept. 29, 2002, Alexander ran behind the line anchored by Jones en route to an NFL-record five first-half touchdowns against Minnesota.

In 2005, Jones helped plow rushing lanes for Alexander's MVP year, during which he amassed a Seattle-record 1,880 rushing yards and what was then an NFL-record 28 total touchdowns. That season ended with Seattle's only Super Bowl appearance — and with Jones' offseason training regimen of pushing trucks in the stifling summer heat of the South gaining national attention.

Through it all, Jones impressed Seahawks teammates and employees with his humility.

The best testament to Jones' value to the Seahawks may have come in the last two years.

While Jones missed the final weeks of the 2008 season and all of 2009 following microfracture knee surgery and a follow-up procedure, three-time Pro Bowl quarterback Matt Hasselbeck had the worst statistical and most injury-filled seasons of his career.

Seattle tried four left tackles in Jones' place last season. They all struggled.

The Seahawks are 9-23 since Jones' last full season in 2007.

Jones tried to return from the microfracture surgery for training camp last summer. He made it through a couple of practices, then had arthroscopic surgery on the left knee in August. He later went on the injured reserve list. His pain was exacerbated by a kidney condition diagnosed when he was a rookie that keeps him from taking anti-inflammatories to combat swelling and pain.

He acknowledged in January that his knee still had a long way to go to get back to playing shape following months of rehabilitation in Florida.

I understand my age, and what I'm coming back from," Jones said then. "And the reality is that if it's over, I can accept that. ... I've had a great career.

Hasselbeck posted a team video tribute to Jones on his Twitter page minutes after Thursday's announcement.

The title? "thankyouwalter.