The trade was part of a three-team deal that saw the Phillies acquire pitcher Roy Halladay from the Blue Jays for three Minor League players and cash.
"We've acquired a very, very nice piece to help this organization move forward," Seattle general manager Jack Zduriencik said. "It's going to be exciting to watch him pitch at the top of the rotation with Felix Hernandez.
"You're always looking for pitching. In this case, a left-hander, in this ballpark with our defense and what he's accomplished ... it was exciting to be able to acquire him. We're happy this was able to come to fruition."
Zduriencik met with Phillies general manager Ruben Amaro Jr. at the Winter Meetings, and the two started discussing a potential deal. The two even talked on Thursday at the airport in Indianapolis where they "shared some ideas."
"When Ruben and I connected at the Winter Meetings, I knew he was after Halladay," Zduriencik said. "He said, 'Look if I'm able to do Halladay, would you be interested in Cliff Lee?' I said I would."
The big question is what will the Mariners eventually do with Lee, 31, who is set to make $9 million in 2010 in the last year of a contract extension he signed while with Cleveland in 2006?
Will the Mariners attempt to sign him to a long-term contract or will they be satisfied to see how he fares back in the American League and address that issue later?
Zduriencik said that there were no discussions about a contract extension with Lee at any point.
"We didn't want to upset the apple cart," Zduriencik said.
For now, though, the Mariners have another frontline pitcher at the top of the rotation.
Hernandez went 19-5 with a 2.49 ERA in 34 starts for the Mariners last season and finished second in the American League Cy Young Award voting behind Zack Greinke of the Royals.
At the Trade Deadline, Lee, the 2008 Cy Young winner while with the Indians, became the award's sixth reigning winner to be traded either in the offseason or during the following season.
Lee went 7-4 with a 3.39 ERA in 12 starts after the trade and was 4-0 with a 1.56 ERA in five postseason starts. The lefty was a monster in the postseason for the Phillies, defeating the Yankees twice in the World Series.
Lee has a career record of 5-1 with a 3.49 ERA in eight appearances -- including seven starts -- at Safeco Field, all coming as a member of the Indians, and has posted a 90-52 record with a 3.97 ERA in his eight Major League seasons. Over the last two, he has combined to go 36-16 with a 2.89 ERA in 65 starts.
In the deal, the Mariners surrender Aumont, their No. 1 Draft pick in 2007. He was 2-6 with 16 saves and a 3.88 ERA in 2009 between Class A High Desert and Double-A West Tennessee.
Gilles, who, like Aumont, is 21, hit .341 in 124 games with High Desert. He was a 25th-round pick in the 2006 Draft.
Ramirez, 21, was 8-10 with a 5.12 ERA with High Desert. He originally signed with the Mariners as a non-drafted free agent in 2005.
Also on Wednesday, the Mariners announced the signing of amateur shortstop Pedro Okuda, 19.
The 5-foot-10, 160-pound left-handed hitter was born and raised in Marília, Brazil, but attended high school in Japan.
Okuda is expected to join the Mariners' Venezuelan academy after high school graduation in the spring and will play there during the 2010 season.