In an off-season trade, the Seattle Mariners acquired Green from the Rockies for pitcher Aaron Taylor, and Green flourished in the Mariners farm system, logging a Texas League-high 14 saves and posting a 2.96 ERA for the San Antonio Missions in 2005 before being promoted to the Triple-A Tacoma Rainiers.

His spring training performance and 4–0 record and 1.38 ERA as the Rainiers' closer caught the eye of Mariners manager Mike Hargrove.

Green made it to the big leagues when the Seattle Mariners called him up on April 29, 2006, to replace reliever Julio Mateo.

When Mateo was activated on May 20, it was thought that Green would return to Triple-A Tacoma, but the Mariners opted to instead send down pitcher Emiliano Fruto.

[1] Despite hype for Green, he struggled in his first year and was eventually demoted to the Mets minor league, AAA affiliate.

Green allowed 21 runs in 27.1 innings at the AAA level for the Rangers, he was subsequently released on June 3.