Imake many references to statistics I use in evaluating baseball players. This sometimes invites questions from readers who want to know how I calculate these numbers or where they can find them.

So I'm going to try something new and lay out my toolbox. Here are the attributes I look for in each type of player. Some of these traits are statistical, and I'll tell you how I came across the numbers and why I believe they work. In other cases, I like or dislike players for more philosophical reasons and I'll try to explain those, too.

I'm not a mathematician or a full-time fantasy writer. I've borrowed most of this stuff from one place or another. If nothing else, I hope I can be a conduit to get you to the best sources of data. Here goes.

I start with a few questions about hitters. How much power does the guy have? Are there any trends in his ability to make contact that suggest he won't be able to hit for a decent average? If he has stolen bases in the past, is there any reason to believe he won't do it this year? Was this hitter remarkably lucky or unlucky last year? Is there a change in his ballpark or role on the team that will affect his production? Is he at an age when improvement or decline are likely?

Those are the basics and here are some ways to answer each one.

A lot of fantasy production flows from power. Fortunately, it's a fairly reliable trait. One thing to look for in the best power hitters is a high fly-ball percentage. Guys who consistently hit 30 home runs tend to put the ball into the air at least 40 percent of the time. That doesn't mean all players who hit that many fly balls will hit a bunch of home runs. But if you're considering a young hitter and he's hitting way more ground balls than fly balls, don't expect much power. Ground-ball to fly-ball ratios can be found many places, including the sabermetric section of ESPN.com's stats page.

I don't worry much about strikeouts, because plenty of great hitters swing and miss a lot. That said, an inability to make contact does correlate to low batting averages. In 2006, for example, Ryan Howard hit .313 but put the ball into play in only 69 percent of his official at-bats. That told me his batting average would drop. He made contact even less often in 2007 and sure enough, his average fell to .268.

Conversely, fellow young slugger Prince Fielder made contact almost 80 percent of the time in his first two seasons. That tells me he's more apt to combine high averages with great power.

Those who contend for batting titles usually make contact at least 80 percent of the time and often push 90 percent. This is an easy number to calculate. Simply subtract strikeouts from at-bats and divide the result by at-bats.

As for stolen bases, I'm wary of guys who don't hit well enough to keep themselves in the lineup consistently and of players with nagging injuries. Former Oriole Corey Patterson is a perfect illustration of the first problem. He stole 37 bases last year but given his .304 on-base percentage, it's hard to imagine teams will continue to give him 400-500 at-bats. Rafael Furcal in 2007 is an illustration of the second problem. Many owners paid big bucks for Furcal, thinking he was good for 40 steals. But a sprained ankle in spring training threw off his running for the entire first half. In a nagging injury situation, steals are often the first statistic to go south. So keep an especially close eye on news about your speed targets.

For questions of luck, I look to batting average on balls in play (BABIP.) This number is often the culprit behind unexpected dips and climbs in batting average. It's not that every hitter should have the same BABIP. Guys who hit a lot of line drives, for example, tend to rank high in the statistic. It's more that, once a hitter establishes a BABIP range, sudden decline is often attributable to bad luck, nothing more.

Jermaine Dye is a perfect example. In 2006, he hit .315, largely because he hit .330 on balls in play, much higher than the .290 to .300 BABIP range he was used to.

In the first half of 2007, his BABIP plummeted to .250 and his batting average fell right along with it. Dye wasn't swinging and missing more than usual. He wasn't in some huge skills slump. He simply went from being unusually lucky in 2006 to unusually unlucky early in 2007. He reverted to his normal career levels in the second half, and I'd expect something like that in 2008.

BABIP is also easy to calculate. Subtract hits from home runs, then divide that by at-bats, minus home runs, minus strike outs, plus sacrifice flies. For a handy reference that includes those plus most of the other numbers mentioned here, you can but Ron Shandler's 2008 Baseball Forecaster. For some sophisticated analysis involving BABIP, check out Marc Normandin's work at BaseballProspectus.com

If you want to see how ballparks affected offense in 2007, go to sports.espn.go.com/mlb/stats/parkfactor. For more elaborate park breakdowns, I favor The Bill James Handbook 2008, available in most major bookstores.

As for age, it's pretty simple. History tells us that offensive players improve through their early 20s, peak in their late 20s and begin a decline that steepens rapidly in their mid-30s. Power and batting eye peak later than speed and batting average. If a guy holds his own in the majors at 22 or younger, he has a good chance to become a star. Conversely, a good rookie year at age 26 promises less, because the player is already near his peak.

Gosh, I'm out of space and I haven't gotten to pitchers. We'll do that in a week or two.

childs.walker@baltsun.com