Jason Varitek, the longest tenured member of the Red Sox and catcher of two World Series-winning teams, will announce his retirement on Thursday in Fort Myers, Fla., a major league source confirmed Monday.
Varitek has been offered a position within the organization, but it is unclear whether he will accept it, the source said.
Varitek, who turns 40 on April 11, was offered a minor league contract and an invitation to big league camp by the Red Sox but has not been at the team's training facility. He has been with the Red Sox since his trade from Seattle in 1997 and retires having played all 1,546 games of his major-league career with Boston. His 1,488 games caught is a club record.
Red Sox pitcher Jon Lester wrote on his Twitter account: "Can't believe Tek is retiring. Such an HONOR to have him behind my plate all these years! Awesome man & amazing teammate."
Varitek last season signaled a desire to continue playing for at least a few more years, and fellow catcher Jarrod Saltalamacchia said earlier this spring that Varitek has been catching, throwing and hitting all winter.
But Varitek, a free agent who served as the Red Sox captain, has not been offered a big league job by another club.
Varitek's decision was first reported by the Boston Globe.
Of players on last year's team, only Tim Wakefield had been with the Red Sox longer than Varitek, and Wakefield, 45, announced his retirement earlier this month.
That leaves David Ortiz, who signed with the Red Sox in 2003, as the club's elder statesman. When asked what it felt like to not have Wakefield and Varitek around after reporting to camp last week, Ortiz said, "It was kind of weird walking into the clubhouse and not seeing them.''
"Tek is somebody, I think, this organization is going to need forever, especially now that he's going to retire," Ortiz said Tuesday. "He's the kind of person this organization needs to keep very close because this guy does nothing but add things, good things. It was an honor for me to be his teammate. I learned a lot of good things from Tek, but the most important thing was hard work.
"His preparation was so good, it was ridiculous. He was a guy that, as long as I watched him play, he wanted to do well, he wanted to be prepared for that.
"Hopefully he feels good about it. Hopefully he's being honest with himself. Man, I'm going to miss him."
Red Sox principal owner John Henry said in December he "absolutely" would like Varitek to remain in the organization in some capacity, and general manager Ben Cherington said, "Our hope is that Tek will always be a part of the Red Sox in some way."
Varitek was acquired with pitcher Derek Lowe from the Mariners in 1997 in exchange for reliever Heathcliff Slocumb, one of the best trades in Red Sox history.
Varitek joined a franchise that hadn't won a World Series in almost eight decades and became a pivotal part of two championship teams. One of the enduring highlights of his career for Red Sox fans came on July 24, 2004, when Varitek shoved his glove in Alex Rodriguez's face during a brawl with the Yankees at Fenway Park.
That moment became a flashpoint in the Red Sox's season, which culminated with the team overcoming a three-game deficit against New York in the AL Championship Series en route to their first title in 86 years. Varitek, who became a free agent after that season, re-signed with the team after a protracted negotiation and was given a uniform with a "C" on its chest, making him the team's first captain since Jim Rice.
The Red Sox won the Series again in '07 with another solid year from Varitek. But since then, he has batted .218, including a .220 average last year while appearing in just 68 games.
While Varitek's game-calling continued to be praised by Red Sox pitchers, his ability to stop base stealers deteriorated. Varitek threw out just 14 percent (12 out of 85) last season, while Shoppach nailed 41 percent of base-stealers (18 out of 44), tops in the American League.
Josh Beckett, for one, has said that he was at his best with Varitek behind the plate.
"I loved working with him," Beckett said. "I've never had a catcher, before (Varitek), who cared about wanting me to be successful, even before he wanted to be successful. He's going to be missed a lot in the clubhouse and on the field."
Information from ESPNBoston.com's Joe McDonald was used in this report.