Mills, 25, is a semi-surprising DFA casualty for the Royals, as he made his MLB debut in 2016 on the heels of a solid season split between the Double-A and Triple-A levels. In 125 2/3 minor league innings, Mills logged a 3.22 ERA with 8.7 K/9 against 2.2 BB/9. While the former 22nd-round pick showed better in Double-A (2.39 ERA) than in Triple-A (4.19), his K/BB numbers at each level were both solid, and they were accompanied by roughly league-average ground-ball tendencies.
MLB.com has yet to issue its newest list of top Royals prospects, but Mills rated eighth among Kansas City farmhands on their most recent iteration, which was updated throughout the 2016 season. He didn’t crack the organization’s top 15 prospects, as recently laid out by ESPN’s Keith Law, but Fangraphs’ Eric Longenhagen did note him just outside the Royals’ top 20 back in December. Longenhagen writes that Mills is “purely a relief prospect,” noting that he could be a solid middle relief piece or a sixth starter/long man. Baseball Prospectus’ Jeffrey Paternostro didn’t include Mills in the top 10 but praised his above-average sinker.
While Mills isn’t a standout prospect, he seems like the type that could very well end up claimed if exposed to waivers, so perhaps the Royals will be able to generate some trade interest. Mills does have two minor league options remaining, which should add to his appeal.