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Finding Fallers with xFIP and ERA

Within this Internet blog post, you will find a list of starting pitchers with the largest negative gaps between their ERAs and their xFIPs. Let's see if we can spot some guys headed for a fall.

Chicago Cubs v St Louis Cardinals
No, that's not Jake Arrieta, it's the other bearded Cubs starter, Jason Hammel. He may be due for some bad regression.
Photo by Dilip Vishwanat/Getty Images

If you read my post from last week (here), you can skip to the table and discussion section below. If not, the next few paragraphs will introduce what I am trying to do here.

If you've been reading any of my work, you know I love tables. I love stats and I love organizing them into nice tables. Today's post is about a big table. We all know and love good old ERA as an evaluator of pitcher performance. However, it can be very deceptive. A pitcher can have a great ERA even while pitching terribly (low K%, high BB%, lots of hits, etc.) if he strands lots of runners, has an unusual number of balls die on the warning track, or has balls simply bounce right to fielders.

On the opposite end of the spectrum, a pitcher can be pitching very well (at least the things he can control) and have a terrible ERA. David Price this season is a great example. His ERA does not really show how dominant he has been with regards to strikeouts and walks. What usually happens in those cases is that the ERA starts to get closer to his "true" ability level as the season goes on. We are seeing that with Price. His last few starts have been much better in terms of ERA and I expect that to continue.

xFIP is a stat that tries to filter out things a pitcher can't control (BABIP, HR/FB ratio, etc.) to come up with an estimate of their "real" ERA. There are certainly some flaws with xFIP, but it is a much better predictor of future performance than a pitcher's current ERA, so it can be used to see if a pitcher is due for some positive or negative regression.

With all that in mind, here's a big table sorted by ERA-xFIP. There are just the bottom 30 starters on here because I arbitrarily chose to cut it off there. It had to end somewhere. These pitchers are in line for worse performance because their ERAs are much lower than their xFIPs support. Their "real" ERA should be a lot higher than their current ERA. After the table, there will be some discussion.

Jason Hammel 2.17 4.14 -1.97
Drew Pomeranz 1.7 3.63 -1.93
Felix Hernandez 2.21 4.1 -1.89
Nicholas Tropeano 2.86 4.69 -1.83
Matt Wisler 2.93 4.73 -1.8
Jordan Zimmermann 2.52 4.28 -1.76
Marco Estrada 2.76 4.5 -1.74
A.J. Griffin 2.94 4.59 -1.65
Steven Wright 2.52 4.02 -1.5
Martin Perez 3.13 4.6 -1.47
Rich Hill 2.18 3.63 -1.45
Garrett Richards 2.34 3.78 -1.44
Chris Tillman 2.61 4.02 -1.41
Jake Arrieta 1.72 3.08 -1.36
Julio Teheran 2.57 3.91 -1.34
Joe Ross 2.7 4.04 -1.34
Dan Straily 2.98 4.28 -1.3
Jimmy Nelson 2.92 4.2 -1.28
Kevin Gausman 2.7 3.94 -1.24
Chris Sale 2.26 3.48 -1.22
Gerrit Cole 2.79 4 -1.21
Madison Bumgarner 2.17 3.37 -1.2
Jose Quintana 2.22 3.39 -1.17
Mat Latos 4.06 5.19 -1.13
Colby Lewis 3.38 4.5 -1.12
Danny Salazar 2.32 3.41 -1.09
Erasmo Ramirez 2.43 3.5 -1.07
J.A. Happ 3.43 4.48 -1.05
CC Sabathia 3.41 4.4 -0.99
Justin Nicolino 4.37 5.36 -0.99

Just like last time, I'm going to try to group these guys into categories.

Very Good, But Not Quite This Good

This is for starters that should be owned in all leagues and basically started every time out. They are playing a little over their heads right now, but even with regression, they are valuable fantasy assets. This includes some elite aces that have taken a step back this year, but should be fine. There's not much to discuss with this group. They should be fine, even if they won't produce at the same rate going forward.

The list: Drew Pomeranz, Felix Hernandez, Rich Hill, Jake Arrieta, Chris Sale, Gerrit Cole, Madison Bumgarner, Jose Quintana, and Danny Salazar.

Obviously, no one is worried about Arrieta, Sale, MadBum, Quintana, or Salazar. However, Pomeranz has such a huge gap between his ERA and xFIP and has been inconsistent in the past, so there are some trust issues there. Rich Hill's xFIP is fairly average, so maybe he's not suddenly a top 10 starter and there is room for him to fall back.

Cole's given up striking guys out this year, it seems (7.4 K/9), and walking more with fewer grounders than ever before. His velocity is the same, but his swinging strike rate is way down to a measly 8.1%. Without strikeouts and ground balls, he's in real danger of becoming just an average pitcher. I'm very worried about him turning into a 3.5 ERA guy this year if he keeps this up.

King Felix has been in decline for several years now, with declining velocity to boot. Like Cole, his walks are up, his strikeouts are down, and his swinging strike rate is poor. At least his ground ball rate is still excellent. With his very high walk rate (3.7 BB/9) and low velocity, I'm just as worried about him as Cole. I think Felix is quickly becoming a just "OK" pitcher.

Young Guns That Will Probably Fall

This category is for young starters off to great starts this year that have been picked up in most leagues, but who just don't have the skills to keep this up and be ownable late in the year.

The list: Tropeano, Wisler, Perez, Teheran, Ross, Straily, and Jimmy Nelson.

Look, I hate to rain on anyone's parade but the numbers are not in their favor. Tropeano's got the strikeouts, but no ground balls and way too many walks. That will haunt him. Wisler just can't get enough strikeouts and has no grounders to fall back on. Perez has been bad before and will again. He has too few strikeouts and too many walks. Only good luck on ground balls has kept him alive so far.

Julio Teheran has looked much better this year than last, but he's basically been the same pitcher since 2013. His xFIPs: 3.84, 3.76, 3.72, 4.19, and 4.05. Only his batted ball luck really changed from year to year. Add to that the fact that his swinging strike rate is at a career low (meaning his nice K-rate is really smoke and mirrors), and I see a league average pitcher the rest of the way.

Dan Straily will fool you into thinking he is useful. He is not. His strikeouts are nice, but he is walking too many hitters and his velocity (89 mph) isn't high enough to afford those walks. I expect him to be HR-prone and have some disaster outings. The strikeouts are there and legit, but there is too much risk here.

Jimmy Nelson has many of the problems plaguing those above: too many walks and an abysmal swinging strike rate that could crater his already-shaky K%. He's just not fooling hitters as much this year and his contact rates are up across the board. His SIERA sits at 4.18. I'm very worried here.

Young Guns That Can Avoid A Big Fall

These are young, talented pitchers that are marked for regression, but should be much more useful going forward than the previous group.

The list: Joe Ross, Steven Wright, Kevin Gausman

I was surprised to see Joe Ross on this list. He was so good last year and seemed to have lots of strikeouts. The Ks have gone away this year (6.88 K/9). Everything else looks about the same. It is remarkably similar across the board to his 2015 line. His swinging strike rate is still very good, but down quite a bit (11.9% to 10%). I think he is a hold because he is too talented to have a strikeout rate that low. I expect that to come up a little and bring down his xFIP. He has declined from 2015, but should still be startable.

Steven Wright, being a knuckleballer, will always carry some risk since the knuckle ball is a fickle pitch. It's effectiveness depends on the weather and the length of the pitcher's fingernails, among other random things. That being said, the 4.07 xFIP is a little harsh on Wright. I don't think xFIP likes knuckleballers in general. Wright has an excellent 11% swinging strike rate and good K% and BB%. He is penalized for a very low HR/FB ratio and BABIP so far that could swing the other way soon. That's what's driving his high xFIP.  That could happen, and some ERA regression is going to happen, but he is pitching too well to run a 4 ERA this year.

Kevin Gausman is looking like the pitcher everyone loved as a prospect. He actually has lots of strikeout rate upside (11.6% swinging strike rate) and is showing excellent control (5.3% BB%). xFIP sees his high strand rate and low BABIP and puts him a 3.76. I think he will be better than that. This is a breakout season for him and he should be a 3.3 ERA guy going forward.

Veterans To Avoid

These are guys that aren't really young anymore and are playing above their previous performance for the most part. I don't think they have enough stuff to avoid a huge drop off the rest of the year.

The list: Hammel, Zimmermann, Estrada, Griffin, Tillman, Latos, Lewis, Happ, and Sabathia.

Jason Hammel is an interesting case. His strikeout and walk rates aren't terrible, but are worse than the last two years. His swinging strike rate is still good, though, so maybe the K% will be ok. His BABIP is very low and his strand rate is very high, so xFIP sees those returning to average. Further, his HR/FB ratio is way down at 5.8% after sitting in the 12% range for three years. Given that he only put up an ERA of 3.74 with more Ks and fewer walks last year, you shouldn't expect his slightly diminished stuff to do much better than that, like it currently is.

Jordan Zimmermann had a few wonderful years in Washington, but has lost the ability to strike batters out. His walk rate is still elite, but he doesn't have anything else to offer. He's not getting a ton of grounders, he doesn't have a good swinging strike rate, and he's been very lucky on BABIP and strand rate so far. I haven't been a fan for two years and I'm still not going to have him on my teams.

Marco Estrada relies on very low BABIPs to have success. He does get lots of fly balls to keep it low, but many of those turn into home runs. He walks a very fine line. When it works, like in 2015, he can be a valuable member of your rotation, but 2014's 4.36 ERA is always a possibility as well, if the homers pile up. He's a risky option, but he has shown that he can beat his xFIP. I'll let you decide if the risk is worth it.

The rest of these guys have some positives (I love Tillman's strikeouts and swinging strike rate), but their xFIPs all suggest they won't have much value to your team. I think all of them will be droppable, but Tillman has the best chance of sticking around because of his strikeout surge this year. The rest are just fool's gold.

Any of the guys I haven't yet mentioned are not worth the time and probably aren't owned anyway. Tschus!