Because no one actually wants Jon Lester for 6 years, that's just the cost of doing business. In a fantasy world where you can name your duration, most people would probably pick 4 years. This isn't a fantasy world, so most people were hoping for 5 but understanding of 6. When you go to 7 you're now facing a pretty significant chance that Lester is nearly useless for half his contract. Useless? That's not a very strong likelihood. The phrase was "nearly useless," and it's not like it's unprecedented. Look at CJ Wilson. Wilson didn't have nearly the same sustained level of success as Lester has had. Didn't he go from a reliever to 200 inning starter like overnight? I'm not sure how he compares to Lester.