Before I get into this, I should note that I put about as much stock in recent rumors that the Mets are “in on Gio Gonzalez” as I do in any offseason trade rumors, which is to say basically none.
I bring it up only because it calls to light a reasonably interesting question about our faith in certain advanced stats, especially when comparing Gonzalez to Jon Niese, also the subject of nebulous recent trade rumors.
Both pitchers throw left-handed. Gonzalez is a year older than Niese and has pitched 71 2/3 more innings over the past two seasons. Both are set for free agency after the 2015 season, but Gonzalez has Super 2 status, meaning he is eligible for arbitration a year earlier than Niese (ie this season) and should collect substantially more money over the course of the next four seasons if both stay healthy.
(How much more money is very hard to say, both because it’s so difficult to assume pitchers will stay healthy and because, as you will see below, it’s not necessarily safe to assume both will continue performing the way they have so far. Also because I suck at this. But I’m guessing about $15 million more over the length of the contract? Anyone?)
Gonzalez has far outpaced Niese in terms of results the last two seasons. He posted a cumulative 129 ERA+ to Niese’s 89 and finished in the top 10 in the American League in the stat both years.
But by many rate stats, Niese has been just as good if not better than Gonzalez. Gonzalez strikes out a few more batters, but Niese has a way better strikeout to walk ratio. Niese has yielded a slightly higher ground-ball rate across his career but has fallen victim to (or, depending on whom you ask, been the perpetrator of) a much higher batting average on balls in play. Both pitch their home games in parks known for suppressing home runs, but Gonzalez has allowed fewer home runs per fly ball over the past two seasons.
All that adds up to mean that though Gonzalez has pitched to a much better ERA and ERA+ over the past two seasons, Niese has had a better xFIP both years and boasts a lower career FIP.
I have no doubt where I stand on this one, but I’ve tried to stay neutral in presenting the above facts because I don’t want to sway you. Keep in mind the distinctions in likely salary and recent injury history. Pure hypothetical: