Top 25 prospects: Nats' Giolito climbs to No. 1

It's draft season in my world, but it's also my traditional time to make a quick tangent back to the pro side to look at the top prospects still in the minors and rookie-eligible. This list largely resembles my preseason list, but it has a few big jumps and some reordering, thanks to some significant graduations.

A few notes before we begin:

• The rankings are limited to players who still have rookie eligibility. That means they have yet to exceed 130 at-bats or 50 innings pitched in the majors and have not yet spent 45 days on the active roster of a major league club, excluding call-ups during the roster expansion period after Sept. 1.

• When ranking players, I consider scouting reports on players -- usually my own, supplemented with conversations with other scouts and front-office executives, as needed -- as well as performance, adjusted for age and context.

• Finally, to see my previous version of prospect rankings (from March), click here. That's what the previous rank refers to.

lastname1. Lucas Giolito, RHP
Washington Nationals
Previous rank: 3
Current level: Double-A

The Nats' pitching coach at Harrisburg, Chris Michalak, decided to change Giolito's delivery this spring, which produced the subpar results Giolito had in April and early May. Fortunately, there doesn't appear to be any lasting damage to Giolito's stuff or arm -- just a delay in his arrival in the big leagues. He's still throwing hard with the plus curveball he has long had, but it might take a few more turns to get him back to where he should be at this time of the year.