Every year, there seem to be advances in established statistical models or, often, new models altogether. While this is clearly a fastly evolving realm, there are some basic tenets of stat analysis that can help even casual fans better understand prospect evaluation.
Tools vs. Skills
In many ways, the difference between what a scout is able to see in a player and what the statistics tell you is the difference between a tool and a skill. A scout might tell you that Billy Rowell can hit a ball 500 feet (and he did once in high school), but that's inconsequential if he is unable to translate that into performance against professional competition. What this section of the Prospect Evaluation Primer articles is meant to tell you is what statistics are most telling for a young player and how they can combine with scouting techniques to paint a more complete picture.
One of the most basic concepts, but also one of the most overlooked, is placing a player in his proper context. For instance, similar performances can mean drastically different things across the two AAA leagues. The International League, home of the Ottawa Lynx, sees significantly less offense than the Pacific Coast League. Consequently, the same amount of home runs are often harder to come by for an IL batter than for a PCL counterpart. Further complicating matters are the varying effects of a player's home ballpark. For that reason, you'll often see me reference league-wide batting stats and park factors when discussing individual prospects. As an example, it certainly makes Nolan Reimold's .844 OPS stand out a bit when you consider that the Carolina League's OPS barely cracks .700 as a whole.
It's similarly important to note a prospect's age vs. the typical age of his competition. As a rule of thumb, most top prospects are on a pace to see significant major league time by the time they are 23, so you'd like to see them performing well at the following levels/ages:
Most players in these classifications are older than these listed ages, but then again, most players are not legitimate prospects. When a player is even younger than these ages and performing well, you'll often see their name at the top of prospect lists. Of course, there are exceptions. Cold-weather players (players from Canada, New England, etc.) generally develop slower as a result of less exposure to baseball as an amateur. Similarly, tall pitchers generally take longer to get their mechanics straightened out. The fact that a player like Adam Loewen has overcome both of these late-bloomer indicators to pitch a 1 hitter against the Yankees in just his 22nd year is one of the many reasons O's fans should be excited about his potential.
You'll note that I left off short-season leagues, which start only after the June draft. In general, high school draftees will be assigned to the O's Rookie League affiliate in Bluefield. College draftees are likewise assigned to Aberdeen. Although they are considered the two lowest rungs of the (stateside) ladder, it's not uncommon to see a highly touted 21 year old get drafted and only play in Aberdeen that season. They'll often get fast-tracked in their second year and, in some cases, they'll skip over low A-ball entirely. Only a mid-season lull kept Nolan Reimold confined to high A-ball this season and he's considered a relatively raw college product.
Secondary Hitting Skills
Even the most casual fans understand the concept of batting average. What many fail to realize, however, is that it can fluctuate a great deal from year to year with no real underlying change in skill level. A true .300 hitter could very well hit .280 one year and .320 the next with only dumb luck to blame. What's more telling about the impact a young hitter might have are his secondary hitting skills: patience and power. As a rule of thumb, the better hitting prospects will walk in about 10% of their plate appearances, while mashing extra base hits at a respectable clip. In fact, a less known concept is the interdependence of the two secondary hitting skills. Without decent pitch selection, most hitters will be unable to turn their power potential into any results. Conversely, if a hitter is unable to pose any real power threat to a pitcher, it's unlikely he'll get pitched around at higher levels and his walk rate will not carry forward.
Of course, a hitter has to be able to hit for a decent average for his secondary skills to mean much. If a guy can only hit .200 in the show, a hearty .100 isolated discipline (OBP minus BAvg.) still results in him making an out 70% of the time. One statistical indicator of a hitter's batting average being maintainable as he reaches higher levels is his strikeout rate. If he is gong down on strikes more than once a game, a common problem is that he might have trouble hitting off-speed stuff. When he gets to higher levels, where pitchers have better secondary pitches, that could result in more K's and a lower batting average. This is a good example of where a scout and a player's stats could tell you the same thing; such a player is unlikely to carry success at lower levels forward.
Pitcher's ERA vs. Peripherals
By now, many of you are at least somewhat familiar with the notion that a major league pitcher has less influence on whether or not batted balls become hits than previously believed. This is not necessarily true in the minor leagues. What happens is sort of a cream rising to the top scenario, where only pitcher's with the best ability to prevent batted balls from becoming hits ever even see time in the majors. Only between them do differences in that ability become trivial. Obviously, this has implications for how ERA's should be interpreted and despite the caveats I just mentioned, that's often the case in the minor leagues as well.
So what statistics are important in evaluating a young pitcher?
Premium pitching prospects rarely have a strikeout rate of less than one per inning, especially in the lower minors. The demonstrated ability to miss bats is the most important skill in a pitcher. Obviously, it's rare that a pitcher is able to miss bats that frequently in the majors, but you'll find that few successful major league pitchers were unable to do so in the minor leagues.
It's entirely possible to succeed with below average groundball tendencies. Brandon Erbe and Radhames Liz are good examples of premium prospects that do not induce a lot of grounders. Still, it's awful tough for a batter to do much damage if he is pounding the ball in the ground and the ability for a pitcher to force him to try can make up for a less than stellar strikeout rate. A strong groundball:flyball ratio is anything over 1:1 or, in other words, someone who induces a groundball over 45% of the time. When you find a player with groundball tendencies and who can miss bats, you're looking at a statistical profile similar to players like A.J. Burnett, Carlos Zambrano and, umm, Daniel Cabrera. O's prospects that fit that bill include Adam Loewen, Hayden Penn and Garrett Olson.
At the major league level, walks can cripple a pitcher's effectiveness. I'm guessing that most O's fans realize this by now. At the minor league level, it's somewhat less of a concern. Pitchers can learn command, even if you haven't seen much evidence of that this season. Nevertheless, a low walk rate is certainly preferable to high one, but even young pitchers with good command in the minors will often struggle with it in the majors.
These are but a few of the many different concepts we will eventually get into in our journey through the Orioles system, but they should provide a good primer. Statistical analysis can not replace the work scouts do, nor vice versa. With any player, the more information you have at your disposal, the better you'll understand them. Stats might tell you that a pitcher isn't missing enough bats to be effective, but only a scout could tell you it's because he doesn't mix his pitches effectively. In that case, the problem is fixable and there is hope for the player. If the reason is because he throws 85 mph with little movement and no secondary pitches, there is much less hope. In either case, only when you have all the information can you feel confident about rendering a verdict on any player.