The 2019 Tacoma Defiance season was the club's fifth year of existence, previously for the last four seasons as Seattle Sounders FC 2, and their fifth season in the USL Championship, the second tier of the United States Soccer Pyramid. It was the team's second season playing in the Tacoma, Washington. The Defiance are majority owned by Seattle Sounders FC.
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Due to their ownership by a higher division professional club (Seattle Sounders FC), Tacoma is one of 13 teams expressly forbidden from entering the Cup competition.
Numbers after plus-sign(+) denote appearances as a substitute.