Holland is the only member of the quartet with significant major league experience, and he has thrived at times, as shown by his three All-Star nods in Kansas City from 2010-15. He threw 319 2/3 innings of 2.42 ERA/2.23 FIP ball with 12.11 K/9 and 3.52 BB/9 during that span, but August 2015 Tommy John surgery stopped Holland from contributing to the Royals’ World Series-winning run late that year and has knocked his career off course in the ensuing seasons.
Since he underwent his TJ procedure, Holland has recorded a 4.20 ERA/4.02 FIP with 10.21 K/9 and 5.3 BB/9 over 139 1/3 innings as a Rockie, National, Cardinal and Diamondback. But the the former lights-out closer will get a chance to revive his career with the Royals, who signed him to a minor league contract in the offseason.
Zuber, 25, ranked as FanGraphs’ 13th-best Royals prospect in April. The 2017 sixth-round pick climbed to the Double-A level for the first time last season and pitched to a 2.42 ERA/2.95 FIP with 10.38 K/9 and 1.73 BB/9 in 26 innings. Also 25, Mejia saw a bit of major league action last year in KC, but the overwhelming majority of his work came in Triple-A, where he hit .271/.339/.382 in 556 plate appearances. Hernandez, whom the Royals signed to a minor league pact earlier this month, appeared briefly with the Diamondbacks from 2015-16. He batted a paltry .209/.274/.399 in 168 PA last season with Boston’s Triple-A affiliate.