No deal has been announced by the Mariners, and financial terms are not known, though a source indicated it would be for less than $1 million.
Mariners manager Eric Wedge said Bay could be an interesting addition to a team with a young roster that is looking to add a couple of veteran hitters.
"He's a guy we've been talking to, but nothing is done yet," Wedge said. "It's an interesting story, an interesting situation. If you are able to make it happen, you've got to feel good about taking a chance on a guy that has been a great performer at times at the big league level.
"He has some strength with the right-handed bat, he's a high-character guy, a hard-worker, great personality. He's had a tough couple years. If it does come through for us, I think it's a great pickup."
Bay, 34, lives in Kirkland, Wash., not far from Seattle, and played his college ball at Gonzaga University. He averaged 27 home runs and 99 RBIs per season over a six-year run with the Red Sox and Pirates, but those numbers dropped dramatically after he signed a four-year, $66 million deal with the Mets in 2010.
Bay hit .234 with 26 home runs and 124 RBIs in three seasons with the Mets, including a .165 average with eight homers and 20 RBIs in 70 games this year.
Wedge said that if the deal works out, Bay would be looked at as an outfielder and designated hitter.
Bay and the Mets came to an agreement to end his contract about a month ago, with Bay due to receive his final $21 million in deferred payments in exchange for free agency.
The buyout included an agreement that the money Bay received in any new deal would be separate from the Mets' remaining $21 million, so New York will still owe him that full amount.
Bay would join a Mariners team looking for increased offense after finishing last in the American League in scoring for three straight years. General manager Jack Zduriencik said on Tuesday that he could possibly sign two outfielders and Bay figures to be the first of that pair at a minimal salary, with the Mariners still having money to pursue Nick Swisher or Michael Bourn, or add a veteran via trade.
Bay, a three-time All-Star and the 2004 National League Rookie of the Year, would be given a chance to revive his career in Seattle much like former Mets pitcher Oliver Perez, who signed a Minor League deal with the Mariners last year and wound up rebounding with a solid season as a left-hander in the bullpen.