Top 50 MLB prospects update

Byron Buxton had scouts and fans buzzing at the Futures Game. AP Photo/Kathy Willens

At the MLB season's midpoint, just past the signing deadline for drafted players, here is a fresh look at the top 50 prospects still in the minor leagues, including a new name on top.

These rankings are based primarily on upside or ceiling, not on proximity to the majors, so the list includes a mixture of players as high as Double-A or Triple-A and a few who have signed but either have yet to make their professional debuts or who have just a few appearances in the low minors.

Players who have already passed the cutoff for Rookie of the Year eligibility are ineligible, as is anyone currently on a major league roster.

Note: I use the 20-80 grading scale in these comments to avoid overuse of the terms "average" and "above average" across the player comments. On that scale, a grade of 50 equals major league average, 55 is above average, 60 is plus, 45 is fringe or below average and so on.

1. Byron Buxton, CF | Minnesota Twins (age 19)
Current level: High Class A (Fort Myers)
Preseason ranking: 22

I've been a Buxton fan for a while and thought he was the best talent in the 2012 draft, although even I'm a little uncomfortable with the extent of the hype around him right now.