Many people, including myself, have shown shock at the deal the Tigers gave Prince Fielder earlier this week. Most people in the sabermetric community do not believe Prince will produce at a level in line with his contract. I do not think it is likely, but I can set up a plausible forecast that shows him producing nearly exactly market level.
Let's start with Fielder's on-field production. He's projected to have a 5-5.5 WAR season, so let's say we peg 5.5 as his value the next 3 seasons- ages 28-30. We then apply the standard aging curve of shaving 0.5 WAR every year the next 6 years to finish the contract. This gives us 39 WAR and, with 5% inflation, $218.8M of value,just above the $214M he got.
[googleapps domain="docs" dir="spreadsheet/pub" query="hl=en_US&hl=en_US&key=0Ao9rrzDkRGDmdEpjRXVwaXc2VkI3Q3B3ZkhXLTdCQXc&output=html&widget=true" width="500" height="300" /]
This represents a very optimistic projection for Prince, with the 5.5 WAR starting point and him sustaining his peak level of production 3 more years. Players of his girth tend to fade faster than normal, like his father Cecil and Mo Vaughn to name a couple. 5% inflation is also a higher estimate; using 4% inflation takes $9M off the total value.
It is also difficult to produce 39 WAR over a 9-year span, especially when starting during your peak. Fifteen position players have managed to do so since 2003, and only eight of them accumulated significantly more than 39. Out of those fifteen players, nine were 26 or younger in 2003: Pujols, Utley, Beltran, M. Cabrera, Beltre, Holliday, Teixeira, Rollins, and Wright. We are left with A-Rod, Berkman, Ichiro, Jeter, Chipper, and Rolen as age-appropriate comparisons. Berkman is the only one in that group who plays similarly to Prince.
Berkman was 27 in 2003, playing LF, so we already see the athleticism difference that helped Berkman age a bit. He transitioned to 1B half-time in '05 to full-time in '07, where he rated average over the span. It's safe to say Prince won't be average defensively over the life of the contract. Berkman had a 145 wRC+ over the span, while Prince has a career 141 mark. With the defensive differences, Prince would have to be around a 150 wRC+ to equal Berkman, a figure Prince has bested three seasons, so it is possible for Prince to do.
The last point "in favor" of this contract is the marginal value of team wins. The closer a team is to 90 wins, the more they should be willing to spend per win. Before Prince arrived, the Tigers were a 86-90 win team, which is good enough for the AL Central but not to get through the playoffs. Prince puts them at a 90-95 win team, which is competitive in the playoffs. The 4-6 wins Prince provides is much more important to the Tigers than they would be to the Orioles, since he wouldn't even get the Orioles to .500 most likely. This all being said, I personally think the Tigers have a lot of roster problems as a result of this, and it will take a masterful reworking to see the Tigers win beyond 2014.