This is his career leading up to FA:
fWAR
1.1 partial year
2.7
4.0
2.3
4.5
5.9
5.6
Every season his xFIP was under 4. His lowest inning total was 170 in 2009. He averaged 202.2 innings from 10-14.
While he got even better in WSH, he was a really great pitcher in DET and seemed like a very good bet to anchor a staff around for the length of his next contract.