Signed to a $500,000 contract last month, Kuo had a 17.55 ERA in six spring training appearances over 6 ¾ innings. He allowed 13 earned runs and gave up five home runs.
Kuo was an All-Star in 2010 with the Los Angeles Dodgers but struggled last season with a back problem early in the season and missed a month with anxiety disorder. During his standout 2010 season, Kuo as 3-2 with 12 saves in 13 chances and a 1.20 ERA.
By releasing him Monday, Seattle owes 30 days' termination pay, which comes to $81,967.