It seems we have the "ace debate" about once per season. It's a classification without a hard and fast definition. Are there 30 aces? Fifteen? How long do you have to be on the top of your game to earn the classification? Are strikeouts king, or is it about run prevention? How much does durability matter?
We've had this debate on our Twitter account, in our internal site threads, and out in public with people who, for some reason, have stopped inviting us to parties. Sky Kalkman posed this question about two weeks ago, as well:
Sky's Theorem: the group of aces has a half-life of two years. If you're an ace, 50/50 you're one in two years. Anyone want to research it?— Sky Kalkman (@Sky_Kalkman) July 9, 2014
I don't think my efforts here will completely answer his question, but it's a relevant connection given my actual genesis for writing this article.
Last week, Felix Hernandez started the All-Star Game, and Clayton Kershaw was the National League's second in line only because he missed a few starts. Hernandez and Kershaw are the two best pitchers in baseball right now, and they've been right near the top for several years. If you asked me to name which active starters are on track for the Hall of Fame, they'd be two of the three pitchers on the list for sure.
It's the third name, though, that really motivated me to write this article: Justin Verlander. At the end of 2012, no one would argue that Verlander was anything but a true ace. Maybe he wasn't the best pitcher in the league, but you absolutely couldn't have the conversation without him. The Tigers signed him to a huge extension before 2013 ahead of his age-30 season, with Verlander coming off four straight 6+ WAR seasons.
The only risk with Verlander was that he was 30. He had never been injured, his stuff was excellent, and he was seemingly improving his arsenal. Sure the velocity wasn't peak Verlander, but no one maintains velocity like that for very long. If you were going to bet on a pitcher at age 30, Verlander was the safe bet.
Yet two years later, Dave Cameron thinks Verlander's contract is the second least trade-able one in the sport. I think I might rank it slightly better than that, but it's certainly not looking like a good value, even if it isn't a disaster. Verlander isn't gone, and I maintain that he'll be good again once he makes some adjustments, but he went from "best pitcher in baseball" to the thing that haunts every general manager.
Kershaw and Hernandez are younger. Felix is 28 and Clayton is 26. They aren't going over the hill tomorrow, but acehood is fragile. Eighteen months ago the Tigers gave Verlander $180 million, and now he's allowing a crazy number of runs and it's not like his peripherals are great. How long should we expect Hernandez and Kershaw's reign to last?
I understand the definition I'm about to apply is subjective, but we obviously can't agree on a definition, so what are you going to do? I'll be defining "ace" as a FIP- of 80 or better over a three-year period in which the pitcher had 500 or more innings. Essentially, were they 20% better than average for a three-year span in which they threw a solid number of innings?
Let's look at the numbers, but note I've dropped the innings cap for the last group to 400 because we're only in July.
Aces after 2010 (stats from 2008-2010):
|Cliff Lee||- - -||93||667.1||7.23||1.28||0.61||20.6||70||67|
|Roy Halladay||- - -||98||735.2||7.74||1.27||0.78||20.4||62||72|
|Jon Lester||Red Sox||97||621.2||8.72||3.08||0.69||16.6||73||74|
|CC Sabathia||- - -||103||720.2||8.06||2.5||0.71||18.3||70||75|
|Dan Haren||- - -||101||680.1||8.53||1.75||1.02||15.9||80||76|
Aces after 2011 (stats from 2009-2011):
|Roy Halladay||- - -||97||723.1||8.05||1.24||0.7||21.4||61||67|
|Cliff Lee||- - -||94||676.2||8.03||1.37||0.68||19.9||71||67|
|Zack Greinke||- - -||94||621||9.04||2.19||0.7||17.6||81||69|
|Ubaldo Jimenez||- - -||98||628||8.48||3.65||0.57||15.3||82||75|
|Jon Lester||Red Sox||95||603||9.43||3.31||0.81||15||76||77|
|Dan Haren||- - -||102||702.2||8.08||1.6||1||15.9||82||80|
Aces after 2012 (stats from 2010-2012):
|Cliff Lee||- - -||90||656||8.64||1.21||0.82||18.3||72||69|
|Zack Greinke||- - -||95||604||8.67||2.29||0.82||13.3||95||78|
Aces after 2013 (stats from 2011-2013):
|Anibal Sanchez||- - -||92||574||8.95||2.6||0.77||13.5||85||78|
|Doug Fister||- - -||89||586.2||6.78||1.81||0.61||13.3||81||79|
Aces after 2014 (stats from 2011-July 19, 2014):
|Anibal Sanchez||- - -||77||478.1||8.39||2.41||0.6||12.6||80||73|
|Chris Sale||White Sox||73||501.1||9.34||2.03||0.86||12.9||69||74|
Now let's take a peak at the data by pitcher and year ("x" denotes ace for that three-year span):
If you study this chart closely, something pretty amazing emerges. I assume Kalkman developed that theorem without careful study of the data, but it's almost dead on. I grabbed five years of data, which includes just three seasons in which we can evaluate his claim. Yet despite limited data collection and absolutely no effort to align myself with his prior expectations, 14 of 30 pitchers classified as aces in 2010-2012 were aces two years later. That's a pretty great estimate. Kalkman followed up with a brief, differently designed study that offers pretty similar results.
Certainly this method institutes an arbitrary cutoff and obviously can't perfectly capture injuries. Wainwright's Tommy John happens right in the middle, but he's back to being an ace. Greinke fell off the list, but he's close. Verlander is still on the list because he was so good in the early part of the cycle. Haren, Wilson, Sabathia, Halladay, Lincecum, Jimenez, and (maybe) Lester are off for good. Verlander probably will be shortly.
Some aces last, but most don't. If you grab a five-year sample like I did, you're likely to only see three or four pitchers remain aces throughout. Which leads me to believe that if you've already gotten four or five years of ace performance from a pitcher, you probably don't want to invest in them for another seven.
There will always be exceptions, but finding them is quite difficult. On average, you can project ace decay pretty well, but I'm not sure you can do it very well individually.
Yes, I'd have signed Kershaw and Hernandez to their deals too, but the risk of paying a pitcher to be an ace is pretty high. You have to make sure you're getting surplus value at the beginning, or the end is going to crush you.
I hope that someone can pick up from this point and test these findings against more data and more definitions of "ace." I don't mean this to be definitive at all, but I was curious about how long we can expect a pitcher's reign to last. Look back at that list and then nod quietly to yourself about Chris Sale's contract and maybe do your best to forget about Verlander's.
All statistics courtesy of FanGraphs.
Neil Weinberg is the Associate Managing Editor at Beyond The Box Score, the Site Educator at FanGraphs, and can also be found writing enthusiastically about the Detroit Tigers at New English D. Follow @NeilWeinberg44