We've got four Mets prospects...three pitchers and one hitter. I don't have Baseball America's Prospects book for this year, so I'll go with Kevin Goldstein's Top 100 list.
Two of the pitchers, Humber and Mulvey, are not listed in Goldstein's Top 100. They were both in Double A last year. Neither seem likely to crack the list of Top 25 pitchers next year.
The other pitcher, Deolis Guerra, is a kid. He is at the bottom of the Top 100 list. It is conceivable he could crack the Top 25 pitchers. Let's assume he does. Under Wang's system, his expected value is 11.2 WARP over six years, and the savings over a free agent add another 8.4 WARP for six years, so that's 19.6 in expected WARP value for Guerra.
Carlos Gomez, the young center fielder, is higher on Goldstein's list. It seems likely he could crack the Top 25 hitting prospect list next year, but he does not look like he'll be projected as a Top 10 guy. That's another 31.7 in expected WARP value.
So, if Gomez and Guerra are #11-#25 prospects as hitter and pitcher, respectively, and Humber and Mulvey do not crack the Top 25, Santana has to be worth 51.3 WARP over the next six years.
BP has not released PECOTA projections for this year, but last year's remain available. BP only projected five years from 2007-2011. From the years 2008-2011, Santana was expected to generate WARP of 23.3, as follows: 7.1, 6.2, 5.0 & 5.0. For 2012, let's assume another 5.0, and for 2013, let's assume a little decline, since he'll be 34 years old. Call it 4.5.
That makes Santana worth 32.8 over the six years. That seems to give the Twins a significant edge. It does, however, assume that Gomez and Guerra end up as top 25 prospects. Let's say Gomez has a 50% chance of being a Top 25 prospect, and Guerra has a 25% chance. The expected WARP for those two would now be 20.75, and the Mets win the trade (subject to the additional caveat below about Humber and Mulvey).
Maybe PECOTA is off and Santana will be better. But keep in mind that in the last six years, Santana has provided 54.0 of WARP, and that's during his prime! If he performs at that same level, the Mets win the trade.
Keep in mind that the scenarios showing the Mets winning are without any data about what prospects outside the Top 25 are worth. They are worth something, even if it is a long shot. Mulvey and Humber have some expected value that we'd need to add onto the Twins side of the equation.
Long story short, if Gomez and Guerra become Top 25 prospects next year, it looks like the Twins win. If Gomez does and Guerra doesn't, it's close to break even for the Twins, subject to whatever value Mulvey and Humber have. If Guerra does and Gomez doesn't, the Twins lose.
It's not as obvious a win for the Mets as I would have thought...at least using Wang's analysis.
One other point is required, and Wang mentions it too. Despite all the math, Santana is not just a star...he's a big star. He can win the Mets a couple of championships. All of the Twins guys can contribute to a team, but they cannot carry a team. If the Twins got three minor contributors and an everyday player, or even two of each, they may add up to a star's value. However, the star brings something more than raw value to the equation. The star pushes you over the edge towards a championship.
