The Mariners optioned Sweet to Triple-A Tacoma on Wednesday.
Sweet will cede his spot on Seattle's 26-man active roster to right-hander Emerson Hancock, who had his contract selected from Double-A Arkansas in advance of his first MLB start Wednesday versus the Padres. After getting called up from Tacoma shortly after the All-Star break, Sweet made just two relief appearances for Seattle, giving up two earned runs over two innings.