WAR is not the Holy Grail of statistics.

It's a conversation starter, not a conversation ender. It's important, it's useful and most of all it's fun. It's the best tool for comparing players across positions or across eras. It's a great tool for evaluating a player's contribution during a season. Maybe it doesn't settle debates; but it helps us get closer to answers.

A quick digression. WAR stands for wins above replacement. Many of you are familiar with it, of course, and the Baseball-Reference.com version of it is now available on ESPN.com's stat pages. (There is also a leaderboard available on the MLB home page.)

What is WAR? It attempts to evaluate a player's total contribution -- batting, fielding, baserunning, pitching -- to his team. It is expressed in terms of wins over the perceived value of a replacement-level player at each position, essentially a Triple-A player. (A team of replacement-level players would be expected to win about 50 games.)

Is it easy to calculate? No. It's true that you need an advanced degree in Programming and Ballpark Effects if you want to figure it out. But is it easy to grasp? I believe it is. Wins is a currency we can all understand. Compare it to, say, the original Holy Grail of baseball statistics: batting average. Do you really know the difference between what .326 means or what .289 means? (That's 20 hits over 550 at-bats, by the way, or less than one extra hit per week.)

But wins ... we know what those are. So WAR attempts to take everything a player does with all the complicating factors -- ballpark effects, different eras, different positions and so on. If we're comparing Carl Yastrzemski in 1968 (.301/.426/.495) to Larry Walker in 1997 (.366/.452/.720), how do you do that? Ten runs produced in Fenway Park in 1968 were much more valuable than 10 runs produced in Coors Field in 1997. Yaz played left field (very well) and Walker played right field (also very well). As it turns out, the two seasons were very similar: Yaz rates at 10.0 WAR, Walker at 9.6. So if you had a lineup of replacement-level players in 1968 and replaced one of them with Yaz, that team would go from roughly 50 wins to about 60.

Anyway, this piece isn't a straight primer on WAR. You can get that from Baseball Reference, which is providing us with WAR. (FanGraphs has a slightly different of WAR, which places a greater emphasis on peripheral stats.)

WAR isn't perfect. It shouldn't be taken as the dogmatic, absolute answer to questions. (Player A's WAR is 2.3 and Player B's is 2.1, ergo Player A is better!) It can certainly be too easy of a crutch in player evaluation at times, but use it wisely.

I've been asked a lot about WAR in my chats, and I figured I would expand on some of those questions to help further explain WAR.

Ben (Charlotte): How would you rate Prince Fielder's season? Power numbers seem a little bit low, but batting average is up and top 10 in OBP/RBIs.

Fielder is hitting .305/.388/.500 with 15 home runs, ranking seventh in the American League in on-base percentage and 20th in slugging percentage. That certainly makes him one of the better hitters in the league -- ninth in runs created and 11th in runs created per 27 outs. Yet his 1.5 WAR ranks him just 45th among AL position players, behind such luminaries as Brendan Ryan, Dustin Ackley, Michael Saunders and Kyle Seager (yes, I just named four Mariners). Why? Remember, WAR judges everything. Fielder is a poor baserunner (one run below average), a lousy fielder (six runs below average) and Comerica Park rates as a slight hitter's park this season. Factor in that first basemen are expected to produce big hitting numbers and Fielder's bat alone isn't enough to make him a great player this season (as of now).

Wait, Josh Reddick rates as the No. 3 position player in the American League. Does that really pass the sniff test?

It does. Reddick rates at 3.9 WAR, behind Mike Trout's 5.2 and Robinson Cano's 4.8. No arguments with those two players. (The top three in the NL are David Wright, Andrew McCutchen and Joey Votto. Again, that makes sense.)

But what about Reddick? Well, he's hitting .272/.349/.531. That's nearly an identical OPS to Fielder, albeit with less on-base skill and more power. His raw batting stats are worth about the same as Fielder's, but then you adjust for putting up those numbers in Oakland, a tough park for hitters. And since he's a right fielder, his production is more valuable -- he's outhit his fellow right fielders more than Fielder has outhit his fellow first basemen. Reddick also rates as an excellent fielder (behind only Ichiro Suzuki in defensive runs saved among right fielders, the defensive metric Baseball-Reference uses). Here's a great catch, another great one (both off Nelson Cruz!) and an awesome throw. Hey, the A's are only a half-game worse than the Tigers; Reddick has been a big reason.

Speaking of Mike Trout, WAR could be used to determine how historical a season he's having, right?

Yes. This is what I mean when suggesting WAR is a terrific conversation starter. I wrote about the greatest rookie seasons of all time the other day. You can check out that list. Here's another one. Using Baseball-Reference's Play Index, we can search for the best seasons ever by a 20-year-old since 1901:

1. Alex Rodriguez, 1996 Mariners: 9.2 WAR

2. Al Kaline, 1955 Tigers: 8.0 WAR

3. Mel Ott, 1929 Giants: 7.3 WAR

4. Ted Williams, 1939 Red Sox: 6.6 WAR

5. Ty Cobb, 1907 Tigers: 6.6 WAR

6. Jason Heyward, 2010 Braves: 6.3 WAR

7. Vada Pinson, 1959 Reds: 6.3 WAR

8. Mickey Mantle, 1952 Yankees: 6.3 WAR

9. Frank Robinson, 1956 Reds: 6.2 WAR

10. Mike Trout, 2012 Angels: 5.2 WAR

As you can see, Trout is already 10th on the list even though we're still in July, moving past Ken Griffey Jr. and Johnny Bench. He's clearly having a historic season, even if he's merely replacement level the rest of the way (which, umm, seems unlikely). Anyway, WAR allows us to compare shortstop Alex Rodriguez playing in a big offensive era in 1996 to Trout, playing in more of a pitcher's era in 2012. Like I said: conversation starter. Begin your debate.

Speaking of good debates ...

Brian (Mexico): In terms of total career (ignore fame and aura) I consider Chipper Jones the superior player to Derek Jeter. Jeter has more hits because he's been a leadoff batter and has fewer injuries, but Chipper gets on base more, has a lot more power and better defense. What do you think?

Before we get to their career WAR totals, let's look at their offensive totals. Chipper has created about 1,933 runs while using 6,502 outs; Jeter has created 1,801 runs while using 7,553 outs. So, fewer runs and more outs. While Chipper has been the better hitter, in terms of value, they're actually pretty similar. When adjusting for position, Jeter's offensive WAR is 89.3 and Chipper's 83.1. Position is everything. There's a reason teams never want to move a prospect to a less important defensive position unless forced to.

However ... Chipper's career WAR is 81.3 and Jeter's 67.9. As you may be aware the defensive metrics have never liked Jeter's defense, so he loses a lot of value there. Again, conversation starter. Maybe you believe Jeter's defense is unfairly rated, or you'd like to factor in his postseason accomplishments or some other intangibles (not that Chipper falls short there) or you just think having a first-ballot Hall of Fame shortstop is more important than having a first-ballot Hall of Fame third baseman.

OK, since you brought it up. Hall of Fame ... Jack Morris? In? Out?

Oh boy. Do we have time for this? Morris' career WAR is 39.3 (here's the leaderboard), below the standard of most Hall of Fame pitchers. I'm not going to debate Morris here, but this is a chance to opine on a couple of beefs I have with WAR.

One, it's my opinion that WAR shortchanges pitchers with durability. I'm not necessarily saying that applies to Jack Morris. But take, for example, Roy Halladay. When figuring his WAR, you're calculating his value over a replacement-level pitcher, maybe a pitcher with a 5.00 ERA or whatever that level is these days. But a Triple-A pitcher isn't going to give you seven or eight innings every start like Halladay does, and certainly not 233 innings like Halladay gave the Phillies in 2011. But WAR, the way I understand it, sort of assumes that's the case.

Another beef. While WAR is league, ballpark and context neutral, ultimately players are compared to their peers. This creates a minor issue in comparing players across generations. As Bill James once wrote when comparing the greatest outfields of all time, "There appears to be a bias in this method toward older teams, since baseball was less competitive a hundred years ago, and the best players were further from the average then they are now."

What James is saying is that it was easier for the early standouts -- Ty Cobb or Babe Ruth or Rogers Hornsby -- to stand out over their peers because the peers weren't as good. Yes, Ruth dominated his time more than Albert Pujols dominates his time. WAR can't account for the fact it's more difficult for Pujols to rise above his peers than for a star player 100 years ago. So I like to make a bit of a mental timeline adjustment when the debate warrants.

But that, I suppose, is a minor flaw. Mike Trout ... well, he's doing just fine rising above his peers.