Sarah Braunstein crunches baseball numbers with Joe Sheehan from Baseball Prospectus

	Roy Hallady is having an All-Star-caliber season, even though his record is 3-5. Icon SMI
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It's only May, but Major League Baseball is already gearing up for summer. All-Star Game voting is underway and aside from my desire to see the Orioles take over Yankee Stadium, I am totally unprepared to start picking the best of the best. So I sat down with Joe Sheehan from Baseball Prospectus to get an insider's opinion on the most essential stats, and how to determine which players are the best using sabermetrics.

According to Sheehan, the goal of sabermetrics is to look at the stats that "give you a better perspective on how talented a player is based on his own performance, as opposed to things that are heavily dependant on the team around him."

Here are two examples. It's usually thought that a great baseball player will have a lot of RBIs. But to get an RBI you need someone to be on base. A player could hit over .300 but he will only have as many RBIs as his team makes possible. It is similar for pitchers and their win-loss records. A pitcher can pitch a great game and still lose because he needs his whole team to provide the win. These are the kinds of stats that sabermatricians want fans to rely on less. Instead, says Sheehan, we should use the stats that tell how good a player is, no matter how his team plays.

In terms of pitchers, Sheehan told me to look for guys who "strike out a lot and don't walk many." Toronto Blue Jays starter Roy Halladay for example has pitched four complete games, has 47 strikeouts and only 10 walks. His team's offense has hurt his 3-5 record but he could still get my All-Star vote.

Moving on to hitters, Sheehan gave me five skills that a great baseball player must have. He must have the ability to get on base, hit for power, cover ground on defense, steal bases at a high percentage, and judge the strike zone well.

Based on these ideas I asked him to identify one overrated and one underrated player in the bigs. For overrated he chose Los Angeles Dodgers outfielder Juan Pierre. Pierre hits for average, and steals a lot of bases but according to Sheehan he's missing a lot of skills. "He doesn't draw walks, he doesn't hit for power and he doesn't have a high stolen-base percentage," he says. As far as underrated goes, Sheehan chose Chicago Cubs first baseman Derek Lee. According to Sheehan, "Lee contributes in a lot of ways. He hits for average, he draws walks, hits doubles and plays really good defense."

Sabermetrics includes stats like on-base percentage (OBP) which measures how often a player is on base versus how often he makes an out, and slugging percentage which measures a player's power. A more in depth statistic is VORP or Value Over Replacement Player. This statistic measures how much better a player is than an average player who could play in his place. VORP is measured in terms of runs and assuming that the replacement player would have the same percentage of plate appearances as the actual player. Sheehan explains that every ten runs a player provides above his average replacement is equivalent to a win. So a player with a VORP of 50 would have been responsible for five wins. I would never have expected to be considering Pittsburgh Pirates centerfielder Nate McLouth for the NL All-Star team, but his VORP of 19.3, is the best among outfielders.

The final piece of advice Sheehan gave me is to remember that this early in the season we're still working with a small sample size. "You can't really evaluate a player on a week or two, you need to look at a career," he says. Because "in baseball almost anybody can have a good week or a bad week." I think I'll wait little longer before I make my All-Star picks, but when I do, I'm going to pick them saber-style.

You can find this season's VORP standings and other sabermetric stats at www.baseballprospectus.com.

What do you think about sabermetrics? The best answers will appear in next week's column.

YOUR TURN

Readers respond to last week's column about off-season trades:

"Trade two is a great trade. The Tigers just need time to adjust."
- Mia, Princeton

"You gave the Mets a thumbs up? Santana has been nothing but a mediocre pitcher this year and the Mets are floundering in a division that many thought they would win!"
- Will, Ohio

"The Mets made the wrong choice in trading for Santana because the Twins got some good players."
- Jack, Big Lake

"I think the trade for Miguel Cabrera is best because he has 6 home runs."
- Lucas, Marion