Duffey was optioned to Triple-A Rochester, the Minneapolis Star Tribune reports.
Ricky Nolasco will begin the season as Minnesota's No. 5 starter as a result. Duffey entered spring with almost a lock on a rotation spot, but he struggled with a 7.30 ERA and poor 6:6 K:BB ratio in 12.1 innings. Given his 3.10 ERA with a strong 8.2 K/9 in the majors in the second half of last season, he could be the first starter called up when there's an opening.