The eligible players, including five other Mariners, have 15 days from Thursday to file. Seattle players that did not file on the first day are pitchers Miguel Batista and Erik Bedard, first baseman Russell Branyan and outfielders Ken Griffey Jr. and Endy Chavez.
The Mariners have exclusive contract talks with all of their potential free agents -- including Beltre and Sweeney -- until the 15-day filing period ends.
Beltre enters the free-agent market for the second time in his career. The Mariners lured him to Seattle following the 2004 season, when he batted .334 with 48 home runs and 121 RBIs for the Dodgers.
He never approached those numbers during his five seasons with the Mariners and struggled through two injury-plagued seasons the past two years. Beltre batted .265 with eight home runs and 44 RBIs in 111 games this past season, spending two stints on the disabled list.
"Everything that year went perfect for me," he said of his final year in Los Angeles. "It was one of those seasons when nothing went wrong. I knew it would be difficult to reach those numbers again, but I thought I would do better than I have done."
At the end of his five-year contract, Beltre ranked first in hits (742) and extra-base hits (280) and was second in home runs (101) and RBIs (388) among franchise third basemen. He also captured two Gold Glove Awards, the only Mariners third sacker to win at least one.
"In the beginning, I wasn't happy with my performance," he said. "I think I put too much pressure on myself to live up to my contract. After that, I thought I did OK. I didn't have the numbers that maybe people expected, but I had typical seasons, until this one."
Sweeney spent his past season with the Mariners, resurrecting a career that he thought was finished a year earlier after being released by the Athletics.
He ended up batting .281 with 8 home runs and 34 RBIs in 77 games, mostly as the designated hitter, a position he shared with Griffey.
Sweeney ended the season on a hot streak, batting .354 (17-for-48) in September.
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.