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Twitter was all aflutter with news of a potential Jake Peavy trade from the San Diego Padres to the Chicago White Sox this morning.  Jon Heyman had the first article I saw reporting that it was a done deal as long Peavy waives his no-trade clause.  Nobody knows, yet, however, who will be going from the White Sox to the Padres.  Let's take a look at what value Peavy should provide to the White Sox, and if what they're possibly giving up will be worth it.

How Good Is Peavy?

Jake Peavy is a two-time All-Star and 2007 Cy Young Winner.  He's been at the heart of many a fantasy championship and sports career peripherals of 9 Ks, 3 BBs, and .9 HRs per nine innings, plus a career 3.27 ERA and 3.49 FIP.  Those are ace numbers, no doubt about it.

But how much has PETCO Park helped his numbers?  And how much has he benefited from pitching in the National League, not having to face designated hitters?  PETCO is by far the best pitchers' park in the game, reducing scoring by about 15% over other NL parks.  It's especially helpful to fly ball pitchers, reducing home runs by about 25%.

A quick and dirty park adjustment would increase the number of runs allowed by Peavy by 8% (half the 15% quoted above since only half his starts have come at home).  That yields a 3.54 career park-adjusted ERA.  Switching between the NL and AL typically adds about .75 runs onto a pitcher's ERA, but let's be conservative and call it .50 runs for Peavy.  He's now at a 4.04 adjusted career ERA.

What's that you say?  Using career numbers is unfair?  And ERA is a bad stat.  I agree.  Let's try some other measures of expected performance, and then adjust for park and league like we did above.

• Peavy's Marcel ERA projection for 2009 (which weights the past three seasons' ERAs) is 3.22 and, well, that's not far off his career ERA.
• Weighting Peavy's past three seasons' tRAs at 5/3/2 yields a 3.29 projected ERA, although that's already park-adjusted, so it looks like a 3.79 ERA with the league adjustment.
• tRA* (which regresses a pitcher's peripherals) projects a fully adjusted 4.25 ERA. 
• xFIP, which is like FIP, but regresses home run per fly ball rate to league average (thus possibly accounting for PETCO's large size) projects a full adjusted 4.26 ERA  (I didn't use a further park-adjustment than what xFIP already uses.)

Hmm, there's actually a lot of agreement there.  To be conservative, let's ignore the possibility that US Cellular won't affect Peavy any more than a neutral stadium (even though it might, considering it increases home runs by about 25%) and assume a 4.00 ERA projection going forward, which only tRA would argue is too high.

What Is Peavy's Value?

Given an ERA and innings pitched projections, a starting pitcher's wins above replacement value is actually easy to calculate.  On a team with average offense, we can get Peavy's winning percentage using Pythagenpat, compare him to a replacement-level starter who wins at a .390 rate in the American League, then multiply by full games pitched by Peavy (IP/9).  Using 200 IP as Peavy's projection (that's what he's averaged over the past four years and I'm being generous not regressing), his projected WAR over a full season is 3.8.  That's a borderline All-Star player.

On the free agent market, where wins cost about $4.5M, Peavy can be valued at $17.6M per season, or exactly what he's schedule to make over the next three seasons.  In 2008, he'll earn $8M, providing an excess value of $9.6M.

Assuming the Padres don't kick in any extra money, and we give the White Sox the remaining 140 IP we project for Peavy this year, their pro-rated share of excess value is $6.7M.

How Good Are the Prospects Headed to the Padres?

Nobody knows for sure what the return haul will be and I'm no prospects guru, but thanks to prospect rankings by Baseball America and John Sickels, the research done by Victor Wang, and Erik's application of the research, we have a pretty good guess at the future value each prospect will provide.  Future value is the difference in what their expected performance would be worth on the free agent market over their six years under team control compared to what they'll likely be paid over those six years.

• Gordon Beckham is the White Sox top prospect, a second baseman taken in last year's draft.  He can't be traded until after June 8th, although the Sox could get around that by calling him a PTBNL.  Baseball America ranked him in the 11 to 25 range of all prospects, which provides a future value of $22M.
• Dayan Viciedo is another top hitting prospect, ranked in the 51 to 75 range by BA, with a future value of $12.5M.
• Aaron Poreda is the White Sox top pitching prospect, a left-hander ranked in the same range as Viciedo, but has a slightly lower $11M future value, as pitching prospects tend to be a bit overrated.
• Tyler Flowers is a catching (for now) prospect who came over from the Braves in the Javier Vazquez deal this off-season.  He's in the bottom quarter of BA's Top 100 list, making his future value the same as Poreda's at $11M.
• There are no more prospects of significant value according to BA and Sickels, although Erik encouraged me to mention Brad Allen, whom he thinks Sickels should have graded as a B hitter instead of a C hitter.  Going with the B rating, Allen would provide $5M in future value.
• All other prospects in the system have a future value of $1.5M or less, including Clayton Richard, whom Sickels calls a C level prospect and is 23 years old.  No, I'm not going to count Jose Contreras.

Putting It All Together

In summary, this trade is likely going to be a win for the Padres.  Not only is Jake Peavy overrated based on his home ballpark and league, his salary provides minimal savings over what's typically available on the free agent market.  In fact, Javier Vazquez, who the White Sox traded away this off-season, is a very similar pitcher, and earns less money.

All four of the top White Sox prospects should provide more value than Peavy going forward.  If Gordon Beckham along or more than two of the other top five prospects are included in the deal, it's a huge win for the Padres.  Although, if the White Sox are able to avoid trading any of their top prospects or receive some cash from the San Diego to help pay Peavy's salary, then perhaps the trade could tilt in Chicago's favor

That being said, the White Sox apparently felt like they needed antoher high-quality starter right now, and free agents only sign during the off-season (obviously).  It's perhaps worth paying a price for the convenience of adding a very good pitcher right now, but I'm worried the White Sox will be paying too high of a price.  We'll have to wait and see.  Who doesn't love a blockbuster trade?