Here at the MLB season's midpoint, and with the deadline to sign draftees coming up on Friday, I put together an update of the top 50 prospects in baseball, given that a number of players from my Top 100 in January have graduated to the majors.

In ranking these players, I tend to weigh upside or ceiling more heavily than proximity to the majors. The list includes a mixture of players as high as Double-A or Triple-A as well as a few who have signed in recent weeks but have yet to make their professional debuts.

Players who already have passed the cutoff for rookie of the year eligibility or are currently on a major league roster are not included here.

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. Corey Seager, SS/3B
Age: 21 | B/T: L/R | Height: 6-3 | Weight: 190
Currently at: Triple-A (Oklahoma City)

Seager just turned 21 in late April and has already reached Triple-A, continuing to perform across the board at the plate even though he hasn't fully come into his power. The Dodgers have started to play Seager a little at third base, as that's his ultimate position, but even with his range limitations due to his size, he'd still be an overall upgrade for them at shortstop right now thanks to his bat