Originally Posted by
Willihammer
xFIP needs qualifying for both pitchers in this case. It assumes a league average HR/FB rate, and Shields' has fluctuated more than most pitchers. But Shield's would seem to have noticed since he has found a way to reduce his FB rate and increase his GB rate in the last two seasons in order to minimize the effect of HR/FB variability. For Marcum, some of his value is tied up in Fielding Dependent Pitching which explains at least partly why his ERA consistently outperforms his xFIP. Marcum has 6.5 career FDP wins to Shields' -.5.
The bottom line is Shields would probably require less money, less years, and is trending into a better pitcher while showing none of the possible signs of injury Marcum is showing, namely elbow soreness. Marcum can't even get a qualifying offer from the Brewers, who have money to spend. So even if you don't buy that Shields is the better talent, he is at worst equivalent while being cheaper and less risky.