Curtis was traded to the Mariners on Wednesday along with Jean Segura and Mitch Haniger in exchange for Taijuan Walker and Ketel Marte.
The left-hander struggled during his time in the major leagues in 2016, with same-handed hitters doing major damage against him (.310/.459/.586). He was optioned down in late July and was not among the Diamondbacks' September callups. Still, Curtis is just 24 and the M's are light on lefty relievers. He should compete for a job in spring training.