A DIPS View of the Tigers Starting Rotation
By Matt Snyder
I really enjoy looking at DIPS (defense independent pitching statistics) numbers for pitchers. I think they give a good look at how the pitcher has actually pitched without worrying too much on the outcomes. Some folks find it hard to buy into the idea that pitchers have little control over whether or not a ball hit into the field of play will be converted into an out or not, but I believe the theory has some pretty solid data backing it up.
Anyway, the Tigers haven’t been very good in the ERA department this year, and a lot of that has to do with the quality of the starting pitching. We’ll take a look at the starters (via DIPS) to see whether or not we can expect their collective fortunes to change.
There are a number of DIPS-based metrics one could look at. I personally like to check out three in specific: FIP, xFIP, and tERA. Why these three? First (and perhaps most importantly), they’re all available on FanGraphs.com, and I’m all about convenience. Second, I like the fact that they all do the same thing differently. Each has a strong point, but each probably falls well short of being the one stat to rule them all.
I’ll give a simple explanation of each metric, but check out the FanGraphs glossary if you want more details on FIP, xFIP, and tERA.
FIP (fielding independent pitching) uses only strikeouts, walks allowed, home runs allowed, and innings pitched in it’s formula to approximate ERA.
xFIP (expected fielding independent pitching) uses the same base, but it regresses home run rates to league average.
tERA (true earned runs allowed) includes batted ball types to account for the fact that line drives (for example) turn into hits more frequently than ground balls do.
Here’s what the Tigers starting rotaion looks like in terms of ERA, FIP, xFIP, and tERA:
The ‘Average’ column is simply an average of the three DIPS metrics. Is this “the right thing to do?” I’m not sure, but I just did it. At any rate, if gives us some way to combine the three if we don’t quite know which one to “believe”.
So, what can we glean from this?
Let’s start with Justin Verlander. His ERA looks to be in the reasonable range when compared to the DIPS numbers (especially when we average them), so it’s not fair to say that he’s been either lucky or unlucky. There’s nothing particularly interesting here, so we can pretty much expect more of the same from JV going forward.
Max Scherzer has a pretty interesting line here. We see some significant disagreement between the advanced metrics. Let’s sort it out. FIP says that his ERA ‘should be’ nearly a full run higher than it is. That’s because Max has allowed nearly two home runs per nine innings (1.96) in his four starts. That’s a lot, and FIP throws up a red flag with the elevated number. Moving on, we see that his xFIP number is quite a bit lower. The regressed home run rate numbers that xFIP uses implies that Max is unlikely to continue being this poor with respect to giving up home runs (perhaps he’s been a bit ‘unlucky’ with the big flies). Next comes a large number from tERA. Max has giving up a lot of line drives (21%), and hasn’t gotten many ground balls (only 31%). tERA doesn’t like that distribution.
It’s clear that Max needs to pitch better. These numbers are suggesting that hitters are squaring up on his pitches with lots of home runs and line drives to show for it. He could also stand do bring the number of walks down a touch or two. If not, we may see his ERA creep up a bit.
Rick Porcello looks to be the leader on the staff in ‘unlucky ERA’. An ERA in the 3’s looks like it would be more reasonable than mid to upper 4’s. Hopefully this isn’t just a product of dominating the light-hitting Mariners. He’s elevated the strikeout numbers so far while still keeping the walks and home runs down, and he has a nice GB/FB ratio. That’s exactly what he needed to do. The line drive rate is still a touch high, but i’ll take what I’m seeing for now. If Rick can keep this stat line going, he’s going to continue to see that ERA drop.
In contrast to Porcello, Phil Coke is the leader in ‘lucky’ ERA (walks turned into unearned runs in Seattle). As a starter, he’s posted a 2.08 ERA, but the DIPS numbers figure that will go up (if he continues to pitch as he has) by about two full runs. The FIP and tERA numbers still look pretty solid, but xFIP jumps quite a bit. He hasn’t yet given up a home run (as a stater), but that probably won’t continue all year. The average 4.20 still seems acceptable to me though.
Brad Penny has been bad. Not 8.44 bad, but the DIPS stats tell us that he’s been pitching like a guy with an ERA in the 5’s. That’s quite a bit better, but it’s no where near acceptable. He either needs to start pitching better (not walking more than he strikes out would be a good start), or he’ll end up getting released. I’m not sure how much longer this can last.
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