If you’e reading this, you know what a star pitcher CC Sabathia is today. In each of the last 6 years, Sabathia has qualified for the ERA title with an ERA+ of at least 136. He’s the only pitcher since 1901 with a qualifying ERA+ of at least 130 in each of his 6th through 11th years. (For the rest of this post, I’ll use the term “star season” to mean a year qualified for the ERA title with ERA+ of at least 130.)
But before he became a star, Sabathia was a rotation fixture for 5 middling years, averaging a 107 ERA+ in 195 innings. His best season ERA+ was 122; the other 4 years fell in the range of 100-106. Those first 5 years were remarkably similar all-around: starts ranged from 30 to 33, IP from 180 to 210, strikeouts from 139 to 171, HRs from 17 to 20.
During his early years, many folks in Cleveland and throughout baseball thought it was only a matter of time before he became an elite pitcher. However, the studies I’ve just done studies that suggest that, after 5 years without significant improvement, it was historically quite unlikely that Sabathia would become a star.