Timlin, 42, recently indicated to Red Sox general manager Theo Epstein that he is likely to attempt to pitch again in 2009 instead of retiring.
Epstein told reporters at the General Managers Meetings on Monday night that he had an open discussion with Timlin shortly after the Red Sox were knocked out of the American League Championship Series.
The sides seemed to come to an understanding that Timlin's time is likely up in Boston, with Epstein saying on Monday that there was "a mutual understanding that Boston probably wouldn't be the best fit for him going forward, that there would be other places with greater opportunities."
An invaluable member of Boston's bullpen for several seasons and owner of four World Series rings, Timlin posted a 5.66 ERA in 2008, the worst of his career.
"But what a career that guy had in Boston," Epstein said. "He was really the staple down there for us -- very reliable, very effective, a big part of two World Series teams. We should not let the offseason go by without tipping our cap to him."
In his six seasons with the Red Sox, Timlin went 30-22 with a 3.76 ERA.
For his career, the sinkerballer is 75-73 with a 3.63 ERA.
After winning the World Series twice with the Blue Jays (1992 and '93) early in his career, he rediscovered the feeling of being a champion with the Red Sox, playing a key role on the title teams of 2004 and '07.
Timlin joined Jason Varitek, Curt Schilling, Bartolo Colon, Sean Casey, Alex Cora, Mark Kotsay, Paul Byrd and David Ross as players from the Red Sox who have filed for free agency. All of Boston's free-agent-eligible players have now filed.
The Red Sox have exclusive negotiating rights with their own free agents until Nov. 13. After that, the players will be eligible to sign with any of the 30 Major League teams.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.