What’s an Ace?

Steve from Bush League Ramble makes his debut to look into the world of a teams “Ace”.

It is a term you hear all the time, and probably use all the time, too. But have you ever stopped to evaluate exactly ‘Pitching Ace’ means? Have you ever wondered what exactly a pitcher has to do to be labelled as an ace? In an attempt to find out, I’ve taken a dive into the different applications of the term.

For me, all the different applications of the term fall into two categories. There are player-dependent and team-dependent arguments. You will often hear a player described as his team’s ace. This implies that each team has an ace, and that there are by extension, at any one time, thirty aces in the game. This is a team-dependent argument, because regardless how good or bad a pitcher you actually are, you only have to be the best pitcher on your team to be classed as an ace.    

There is something curious about Gerrit Cole in the context of understanding what makes an ace, especially in the team-dependent versus player-dependent comparison. He has unquestionably been an elite pitcher so far this season, behind only his teammate, Justin Verlander, and Max Scherzer in fWAR to date, whilst striking out hitters at a higher rate than anyone else in the league. But a team-dependent application of the term ‘ace’ would mean he was an ace last year when with Pirates, but is no longer an ace today, despite nearly having produced as much value in just two months this season than he did in the whole of 2017!

Theoretically easier to define than player-dependent approaches, the ‘Team’s No. 1 Starter Argument’ is surprisingly difficult to apply. Simply take the number one, top of the rotation arm for each of the thirty teams, you say? Well, what defines a team’s number one starter? Is it the pitcher who started on opening day? A quick glance at each team’s opening day starting pitchers highlights just how woefully inexact this approach is to defining even a single team’s ace.

Just a few obvious omissions from this list include Madison Bumgarner, Shohei Ohtani, Jacob DeGrom, Sean Manaea, James Paxton and the aforementioned Gerrit Cole, who could all stake legitimate claims of being the aces on most teams in the league, if not their own teams. Overwhelmingly then, I would argue that any true definition of the term ‘Ace’ has to remove the team from the equation, and be player-dependent in nature.   

The consensus gut theory posits that there are never more than ten or so elite pitchers in the game, and that there is generally a consensus on who those guys are. This approach allows for more than one pitcher on a team to be an ace, and satisfies the demands it is solely the player, not the team, that dictates the term, and is probably the prevailing view amongst fans, as evidenced from my rigorous and far-reaching research across social media platforms (OK, OK, I did a twitter poll).

There is absolutely nothing wrong with this view per se, but it sits somewhat uncomfortably with me for the simple reason that it lacks concrete, quantifiable reasoning. Fashion, bias and plain old stupidity can get in the way of producing the consensus. Let’s take the most recent Cy Young award voting as an example – Corey Kluber, Chris Sale, Max Scherzer, Clayton Kershaw, Luis Severino, Justin Verlander and Stephen Strasburg all got Cy Young votes in 2017. So far, so good. But so did  Zack Greinke, Jacob DeGrom, Robbie Ray and Gio Gonzalez. Not to mention Ervin Santana, Alex Wood, Jimmy Nelson and Marcus Stroman, who also did. Which ones are the aces and which the imposters, and which the one-season wonders? What this approach lacks is a coherent, measurable threshold that will decide if a guy is an ace or not.

It goes without saying that an ace has to be really good at what he does, but I wanted to isolate the things that he had to be good at in order to be considered elite. I read lots about how ace pitchers stop losing streaks, find ways to win big games and make their team better, but these are all intangible, and impossible to measure. In addition to that, those arguments feel too team-dependent to hold water. The statistical bars hoops I want ace pitchers to jump through are all as non-team-dependent as possible, so FIP instead of ERA, for example.

Using use the play index, I set filters so that only pitchers who had a sub-3 FIP, a sub-1 WHIP and a minimum 9 strikeouts per 9 innings since the beginning of last season were left standing. Only Corey Kluber, Chris Sale and Max Scherzer fitted the bill, and for some fans that might sound about right, in that they are the only true aces around in 2018. I like to think the field is slightly more open than that, however, and so I played around with the settings a bit, relaxing each threshold by 5-10% until I arrived at the following pitchers.

It is hard to argue with the view that these eight guys represent the current elite class of pitchers in MLB, that these are the ‘Aces’ right now. The best thing about this approach it stands up to historical analysis – slightly adjusting for the different strikeout environment produces a list of Tim Lincecum, Rich Harden, CC Sabathia, Dan Haren, Ervin Santana and Josh Beckett as the aces of 2008, or Roger Clemens, Kevin Brown, Al Leiter, Pedro Martinez, Curt Schilling, Randy Johnson and John Smoltz as the aces of 1998, for example. This approach produces similar results to the ‘gut feeling’ approach, but is just that little bit more robust and bias-free.

So there you have it. What do you have to do to be called an ace? Strike out loads of guys, allow hardly any baserunners, and have an elite FIP, for a whole season or more. Are Gerrit Cole, Aaron Nola and Patrick Corbin aces? Not yet, but if they can keep doing exactly what they are doing until the end of the season and beyond, then I will happily argue that they are. 

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