Lucas, 33, posted a .255/.302/.323 line with five home runs and 37 RBIs in 163 games for the Marlins in 2013-14. He hit .316/.389/.420 with six homers and 48 RBIs in 107 games for Triple-A Round Rock last year.
Lucas would provide depth and versatility, as he played all four infield positions and both corner outfield spots during his time with Miami, and he has played every position except catcher during a 12-year Minor League career.
Mariners general manager Jerry Dipoto said Thursday that his Major League roster was close to being set, but that he'd continue adding competition for the final roster spots.