The Mariners are optioning former top prospect Colt Emerson to Triple-A Tacoma, a source told MLB.com's Daniel Kramer. The club has not confirmed the move.
The 21-year-old had succeeded in plugging holes in Seattle's infield, but struggled to find his footing at the plate in his first stint in the Majors.
Emerson, who the Mariners signed to an eight-year, $95 million extension in March -- the largest contract ever signed by a player who had yet to reach the Majors -- has appeared in 69 games this season as a third baseman and shortstop, hitting .190 with eight home runs and 23 RBIs. Lauded for his hit tool, he also posted an uncharacteristically high 34.4% strikeout rate.
Emerson was promoted and made his debut back on May 17 to take the spot of utility infielder Brendan Donovan on the roster; Donovan's recent return from his nearly three-month absence (left groin muscle strain) gave the club greater flexibility on the left side of the infield, allowing for Emerson to continue his development at the Minor League level.
In the corresponding move, the Mariners are selecting the contract of the club's No. 19 prospect Brock Rodden. Rodden, 26, is hitting .262 with 19 home runs and 65 RBIs in 92 games this season with Triple-A Tacoma.