Milner was reassigned to minor-league camp Friday, Marc Topkin of the Tampa Bay Times reports.
Milner enjoyed a solid spring training with a 3.48 ERA, 0.87 WHIP and 12:0 K:BB across 10.1 innings, but wasn't able to earn a spot on the 25-man roster. The 28-year-old will begin the season at Triple-A Durham but may make his way to the majors when the Rays need to shuffle their bullpen arms.