Before we can get to the point of doing the actual projections however, we need to go over some important concepts.
1) BABIP is a static metric in the sense that .300 is the waterline from which anything above or below would generally be considered lucky or unlucky. However, there are things that can influence BABIP. The easiest to identify and adjust for is LD% (line drive %). It stands to reason that the more line drives a batter hits, the more likely a ball is to fall for a hit. That's because line drives are hit harder than other types of balls, giving fielders less time to react. This is particularly true of hitters with plus power. For every %-point above 20%, we can assume a hitter can maintain a BABIP 8 points higher than average. For example, a career 22% LD hitter should, theoretically be able to maintain a BABIP closer to .316.
After line drives, ground balls are generally the next most effective type of ball in play for hitter, and those batters who are plus or plus-plus runners can utilize the ground ball to cheat the rule of .300 by 5 or 10 points. Luis Castillo is probably the best example of this phenomena that I can think of. Despite a rather pedestrian 18.6% LD rate, his ability to hit ground balls at an astonishing 63% rate, paired with his plus speed led to a career BABIP of .329 that is about as high as you'll ever see. Of course, the GB/speed combo works in reverse - if a batter is slow afoot, he'll generally want to avoid hitting ground balls and instead focus on hitting the ball in the air. Depending on which sort of runner you are, ground balls can have a positive or negative effect on your BABIP, but generally, we consider them to be neutral. But if you have a plus runner you can probably add around 2 points to a hitters BABIP for every % point over 45%.
Lastly, you have the fly ball. Fly balls are the least likely type of ball-in-play to fall for hit. Fielders generally have ample time to read, react, and run down fly balls and convert them into outs. While they are the least likely to turn into hits, they are also the most likely to turn into home runs, so hitting a lot of fly balls isn't necessarily a bad thing if you're hitter with plus power. Think Barry Bonds, who's career 51% fly-ball rate is very high. A further look at the hitters with the highest FB% from last year helps illustrate the point.
2) If you've ever heard someone say that a hitter strikes out too much to hit for a good average, there's a reason for it. Basically, the more you strike out, the fewer balls you're going to put in play. And the fewer balls you put in play, the less likely you are to generate hits. We'll run a quick example of two hitters who each have 500 at-bats, one who strikes out 20% of the time, and another who strikes out 10% of the time - both with a 'normal' .300 BABIP:
|Player||AB ||K%||K ||BABIP||BIP||AVG|
That shows us that strikeout rate negatively impacts batting average. Of course, there is plenty of correlation between players who hit for plus power and strikeout rate. Again, a cursory glance at the Major League leaders in strikeout rate shows a list of all-or-nothing power hitters.
Now that we've covered all of those factors, let's try projecting a player. I think Austin Jackson is a fun one. Jackson is a speedy center fielder who's fantastic defense and .293/.345/.400 production garnered him plenty of well deserved Rookie Of The Year Consideration.
Using what we've learned so far we observe a few noteworthy things. First of all, his .396 BABIP is exceptionally high. But we also see that his 24.2% LD rate was very good, and his 48.4% GB rate should play well for a plus-speed player. We also see that his strikeout rate of 27.% is very high, and likely to negatively impact his ability to hit for average long-term.
So lets run a quick analysis that projects Jackson over the same 675 plate appearances he had last year. Assuming everything else (BB%, HBP, SH/SF), let's 'normalize' his hitting performance.
Since we know each point of LD% above 20% is generally good for 8% of extra BABIP - and speedy hitters who hit the ball on the ground more than 45% of the time generally benefit by about 2 points of BABIPBABIP for Jackson would be 300+(4.2*8)+(3.4*2)= .3402
Subtracting his strikeouts (170) and home runs (4) from his at-bats (618) we're left with 444 balls in play. Using our normalized .3402 BABIP, we can more accurately project him for 151 hits instead of the 'lucky' 180 he produced in 2010.
Presuming his ISO and BB rate remain unchanged, that would leave Jackson as a .251/.305/.358 - .663 hitter. That's likely far closer to Jackson's reality than his production last year, and generally speaking, what you'd expect from someone with a Minor League OPS of just .766.
Of course, players aren't static, and Jackson is still in the 'progression' phase of his career. So lets say you add 5% to his production, which is what you'd expect from someone going from their age 23 season to their age 24 season. You're left with a .696 OPS.
We'll have to see how the season plays out, but I'm guessing that's the kind of mark you'll see from Jackson in 2011. And that's how you can use different metrics to more accurately project future performance.
Corey Ettinger is a proud contributor to both 612Sports.net and 312Sports.com. He also provides extensive analysis of the American League Central Division at his own blog AL Central In Focus.