Rodriguez, 31, batted just .197 in 44 games for Seattle, but came up with some timely hits. He beat the Blue Jays on April 11 with a two-run walk-off single in the ninth inning, and did the same to the Yankees on Sept. 14 with a solo home run in the 12th inning.
Rodriguez also hit a game-winning sacrifice fly to top the Twins in the 10th inning on May 23 in Minnesota.
Rodriguez made the Mariners' Opening Day squad as a non-roster invitee on a Minor League deal and wound up splitting the season between Seattle and Triple-A Tacoma. He started 21 games at shortstop, nine at third base and two at second for the Mariners, finishing the year with two home runs and 14 RBIs in 117 at-bats.
Rodriguez is hitting .270 in 11 games with Tiburones de La Guaira in the Venezuelan Winter League.
The Venezuela native would have been arbitration-eligible, but instead becomes a free agent able to negotiate with any team, including Seattle. Rodriguez has played six years in the Major Leagues, including three with the Twins and two with the Padres.
The Mariners similarly outrighted closer David Aardsma and reliever Jeff Gray earlier this week, with Gray being claimed off waivers by the Twins and Aardsma becoming a free agent. Those two also would have been arbitration-eligible.
The club now has three arbitration-eligible players remaining -- relievers Brandon League and Shawn Kelley and left-handed starter Jason Vargas.
The Mariners' 40-man roster now stands at 36. They'll likely add some Minor League players before Nov. 18 in order to protect them from the Rule 5 draft.