That drop is most likely because Bryce Harper is now a major leaguer, and several of the team's higher-ranked pitching prospects have had arm issues during this past season.
Regardless, it's clear that there's plenty of talent there.
Many of their top-10 prospects are still some time away from cracking the major league team, while others are much closer. Spring training is the perfect time for both to display their skills, and the Nationals will likely give their young guys plenty of opportunities to shine.
On a team that doesn't have all that many holes or position battles to deal with (okay, so second base and catcher may come down to the spring's final week), manager Davey Johnson should take advantage of the opportunity to see what his young guys can do.
The players that perform the best will likely be given September call-ups, so it's important to get to know them while you can still watch them play in spring training.
Note: All prospects listed are ones that are currently in spring training. A complete top-10 prospects list can be found here.