The 2010 Seattle Mariners season was the 34th season in franchise history. The Mariners finished the season with 61 wins and 101 losses. As the Texas Rangers won their first pennant that season, the Mariners became one of only two teams to have never played in the World Series, along with the Washington Nationals.
Offseason
Coaching staff changes
Most of the 2009 major league coaching staff was retained, with the exception of third base coach Bruce Hines. Mike Brumley was named the new third base coach on October 30, 2009. On December 7, the Mariners announced their minor league staff. Eriberto Menchaca, who managed the Class-A Clinton LumberKings in 2009, was moved to the rookie-level Pulaski Mariners, Jesus Azuaje was named manager of the rookie-level Peoria Mariners, Tim Laker was named the manager of the Double-A West Tenn Diamond Jaxx, and Andy Fox was named hitting coach for the Diamond Jaxx.
Roster changes
Key departures
On October 19, 2009, catcher Kenji Johjima, the first Japanese-born catcher in Major League Baseball, exercised an opt-out clause in his contract and returned to playing in Nippon Professional Baseball. The Mariners also lost their home run leader, Russell Branyan, who declined a one-year deal with the Mariners to test the free agent market. Two-time Gold Glove winner Adrián Beltré opted for free agency on November 5, 2009, and later signed with the Boston Red Sox. The third baseman declined $12 million in arbitration from the Mariners only days after the team signed Chone Figgins (see below). Beltre officially parted ways with the Mariners when he signed a one-year, $9 million deal with the Boston Red Sox. Pitcher Phillippe Aumont, noted as one of the top prospects in the organization, was sent to the Phillies in the trade for Cliff Lee. Also, pitcher Brandon Morrow was traded to the Toronto Blue Jays as well. Carlos Silva, whose time in Seattle was plagued by injury, was traded to the Chicago Cubs on December 18.
Major league acquisitions
Chone Figgins signed a four-year contract valued at $36 million. General manager Jack Zduriencik noted Figgins' versatility on defense and could ask him to play second base as well.
Ken Griffey Jr. returned to the Mariners with a one-year deal after a successful 2009 season and large number of Seattle fans asking for "one more year." Shortstop Jack Wilson signed a two-year, $10 million deal to remain in Seattle. Wilson was one of the players received from the Pittsburgh Pirates at the trading deadline in 2009.
On December 14, 2009, the Mariners, along with the three other organizations including the Philadelphia Phillies, the Toronto Blue Jays, and the Oakland Athletics agreed to a 4-team, 9-player deal. The Mariners received former Cy Young Award winner Cliff Lee from Philadelphia in exchange for three prospects as a complement to ace Félix Hernández.
On December 18, 2009, the Mariners traded pitcher Carlos Silva and cash considerations to the Chicago Cubs for outfielder Milton Bradley, particularly noting his offensive capabilities. On December 22, the Mariners traded Brandon Morrow to the Toronto Blue Jays for pitcher Brandon League, and a minor league prospect. The Mariners acquired first baseman Casey Kotchman from the Boston Red Sox in exchange for utility player Bill Hall, a player to be named later, and cash considerations. On January 29, 2010, the Mariner signed outfielder Eric Byrnes to a one-year, $400,000 contract after he was released by the Arizona Diamondbacks. The Mariners signed first baseman Ryan Garko to a one-year $550,000 contract on February 1. On February 6, the Mariners re-signed pitcher Érik Bédard to a one-year, $1.5 million contract, with a mutual option for 2011.
Minor league acquisitions
After the World Series, the Mariners cleared five spots from their 40-man roster after infielder Bryan LaHair, pitchers César Jiménez, Randy Messenger and Marwin Vega were outrighted to the Triple-A Tacoma Rainiers, and pitcher Justin Thomas was claimed off waivers by the Pittsburgh Pirates. The Mariners added seven new scouts after the season including the West Coast Supervisor Butch Baccala, Southern California scout John Ramey, Northwest scout Joe Ross, Midwest scout Tony Russo, Southwest scout Jess Kapellusch, Atlantic scout Mike Moriarty, and Gulf Coast scout Devitt Moore.