Situation: You just lost your first baseman to an injury for 4-6 weeks, and you need a replacement. You check the free agent list and see a bunch of over-the-hill veterans and uninspiring names. How do you choose which one to get? In determining which players to pick up, it’s worth your while to check up on batting average on balls in play (BABIP) and line drive percentage (LD%).

A typical Major League player has a BABIP of around .300, but that varies according to how well he is squaring up the baseball. If he hits a line drive rather than a grounder or a fly ball, he has a much greater chance of getting a hit, thus a high LD% of about 20% translates into someone who is capable of hitting .300, while someone who is around 15% is likely due for an average around .250 or lower.

So picking up a player who is hitting .330 on the year with a low LD% and high BABIP is not a good idea. The law of averages suggests that more of those balls will turn into outs in what’s left of the season, and things will normalize towards their career averages (or true talent). Not always the case, but by and large the mathematics supports this.

So based on this, some good and bad bets for the second half:

It’s all Good (Pick ‘em up)

Paul Konerko, 1B. BABIP of .238 and LD% of 17% suggests that there are good things to come. At least much better things than a .217 average. Hasn’t looked good at times, but this guy hasn’t missed hitting 20 HR (actually 30 HR) since 2003.

Ramon Hernandez, C. Has a 20% LD rate, but a BABIP of just .250. That can’t last very long if he’s healthy. As thin as catcher is, he could help you if drafted someone like Victor Martinez this year.

Robinson Cano, 2B. Sabermeticians have been waiting all year for the turnaround. Still, Cano is a good trade target, with a 19% LD rate and .258 BABIP.

Adrian Beltre, 3B. Another trade target. He’s been smoking the ball al year long with a 25% LD rate, but only has a .259/.329/.440 line and .271 BABIP to show for it.

Edgar Renteria, SS. He’s got a 22% LD rate, but his BABIP is .275 and his line is unimpressive at .254/.300/.326. No power to speak of, but hey, this is shortstop.

Melvin Mora, 3B. His 17% LD rate suggests that the .248 BABIP is due for some upward correction, though he’s 36 and I’m not sure he has enough power to be useful as a third sacker.

Proceed with Caution (Get at your own risk)

Justin Morneau, 1B. A perfect sell high candidate, Morneau’s impressive line is propped up with a .351 BABIP that masks a middling 17% LD rate. Take advantage of owners who watched the home run derby and were impressed.

J.D. Drew, OF. An MVP-like June hides the fact that he’s only hit 16% liners. His BABIP is mildly elevated at .335. Trade the All-Star MVP for something good right now.

Delmon Young, OF. No power, and not much in the line drive department at 15%. His line isn’t that ugly because of his abnormally high .343 BABIP.

Adam Jones, OF. With a BABIP of .354 but a low BABIP of 16%, this rookie is about to crash. Drop him now.

Joe Crede, 3B. His .245 BABIP doesn’t stand to improve much unless his 13% LD rate gets better.