Hays, who was a nominee for Baseball America's Minor Leaguer of the Year award in 2017 after he hit .329 with a .958 OPS, 32 doubles and 32 home runs in High-A Frederick and Double-A Bowie last season, came in at No. 21. He made his major league debut in September and was also the top-ranked prospect in the system according to Baseball America this offseason.
Below him are two other possible impact bats, catcher Chance Sisco (No. 68) and infielder Ryan Mountcastle (No. 71). Sisco, who was the Orioles' only representative on last year's list at No. 57, hit .267 with a career-high seven home runs and a .735 OPS at Triple-A Norfolk. The 22-year-old also debuted with the Orioles in September, and homered twice in limited action.
Mouncastle, 20, hit .314 and had the most extra-base hits in the minors (51) when he was promoted from Frederick to Bowie at midseason and moved from shortstop to third base. The transition proved difficult and he struggled at the advanced level, but there's still confidence in his bat once he finds a position.
On the organizational rankings released in December, Mountcastle was No. 2 in the system, while Sisco was No. 3. [Disclaimer: I wrote and compiled the system rankings, and explained that decision here.]