This is looking at it backwards. Impending free agents are evaluated based on their track record, position, and importantly, their age. The expected WAR for the next year is then calculated, and for each subsequent year of the contract, you factor in .5 WAR decrease. Multiply the total WAR over the going rate per WAR to get the contract. After an off-season, you can calculate the going rate based on what was given out to see if it is increasing. Has been 4.5-5/WAR for a few years. Willingham got 3/21. That's about 4.5-5 WAR. He was probably valued at 2 WAR in 2012, 1.5 in 2013, and 1 WAR for 2013. If players perform badly in their first year of a FA contract, perhaps their WAR valuation was high...or they had a bad year. If anything, it would decrease the going price per WAR. However, with more TV revenue to spend in baseball, I expect the going rate to increase this off-season.