I see players all year long, as amateurs, in pro ball, at the Futures Game, and in the Arizona Fall League. If I've seen a player, my scouting report becomes the foundation of his capsule and his ranking here. I can't see every player, and sometimes only see a player once on a day that isn't representative of his abilities, so I supplement all of my content with conversations with various scouts and with at least one executive with every MLB team who has seen his team's prospects enough to discuss them and suggest how I might rank them.
I refer within player capsules and descriptions to grades on player tools and overall forecasts, using the industry standard 20-80 scale, where 50 is major-league average, 60 is 'plus' or well above-average and All-Star level, 80 is a Hall of Famer, and 20 is the bottom of the scale. You'll see a lot of 55s and 60s, but very few 80s because those are rare skills and the grades themselves should be reserved for the best cases, and very few 20s and 30s because someone with a 30 hit tool or 20 command isn't a prospect.
In some cases, I try to give rough odds of certain outcomes, but otherwise refer to things as likely, very likely, or unlikely simply to make the capsules easier to read. If I say likely, I mean better than 50 percent odds; very likely means better than 75 percent; unlikely means below 25 percent.
I write each year's rankings independently. While it may seem like a player made a big jump or suffered a big drop from last year, that's a consequence of the process, not an input. I didn't look at last year's rankings at any point during this year's writing, and a player moving up or down is not per se indication of a change in his ability, but a reflection of what I believe to be his current value and projection relative to all other prospects.
This is by nature a forecasting exercise -- what I think players will become as big leaguers, and when, and how likely those outcomes are. I'm also balancing the two sides of the player projection coin: probability, how likely is the player to become something more than a replacement-level big leaguer; and ceiling, what is the reasonable best-case scenario for the player if everything works out. If a player has a high ceiling, and I think has a relatively strong probability of reaching it, he's probably in the top 10 or even top five. The remainder of the list is sprinkled with players who have more of one or the other, but I tend to favor prospects with higher ceilings over those with low ceilings but high "floors" -- meaning a reasonable worst-case scenario, assuming the player stays healthy.
"Raw power" refers to the player's physical ability to drive the ball far; "game power" refers to his ability to do it against live pitching, which to some extent incorporates the player's ability to hit and to recognize what pitches he can drive. "Control" refers to a pitcher's ability to throw strikes; "command" refers to his ability to locate his pitches and to make them do what he wants in terms of spin, break, sink, or run. I separate grades for defensive range from arm strength, but if I refer to a player as, for example, a "60 defender," that's referring to his total defensive value, which in the case of a 60 grade would be at least 5 runs saved better than the average for the position.