Just before the season, I unveiled a system for rating starting pitchers by tiers and focused the method strictly on those who earned one of the 30 coveted Opening Day starts across baseball. Though we didn't get into the overall results at that time, that exercise drew upon a mere subset of the data: All starting pitchers were in fact rated, and all were slotted into various tiers against each other.
With the teams on their annual midseason break, a little over half of the schedule has been played (54.6 percent, in fact). That makes it a good time to update the numbers and see who has changed tiers, either to the positive or negative. It also lets us take a snapshot of the first half in starting pitching across baseball.
The tiers are built according to a metric called ACE score, determined by a methodology identical to that laid out in the previously linked piece. All starters are slotted against all other starters since the beginning of the 2014 season, though the tier lines are drawn just for those active in 2017. The general categories being rated are performance, durability, consistency and dominance.
There are six tiers, which can be roughly defined as such:
Bound for Cooperstown
Front of the rotation
Solid No. 2 or 3
Solid No. 3 or 4
Just a guy
Replacement level
Since there are different ways to approach the data and we don't want to dump the whole thing on you, let's go through it FAQ style.
1. Is Clayton Kershaw still on his own tier?
You can be as systemic as you want to be with things like this, but at some point, you still have to decide where to draw the lines between tiers. Before the season, Kershaw's ACE score was so far ahead of everyone that you pretty much had to give him his own tier. It would be easy to make the case that this remains so, but Max Scherzer and Chris Sale have been awfully good.
While Kershaw has improved his ACE score since the start of the season (a 14-2 record and 2.18 ERA will do that, even for him), Sale and Scherzer have improved even more. In fact, of all pitchers in one of the top three tiers before the season, only one has improved more than Sale and Scherzer. (More on that guy in a bit.)
The bottom line is that Kershaw remains the game's best pitcher and he'd have to collapse to lose that status in this system before the end of the season. However, Sale and Scherzer have solidified their own dominance to the point that Kershaw needs to make room, because he's got company in Tier I. Now there are three.
2. Can anyone else get to Tier 1?
Probably not. The drop-off from Scherzer at No. 3 (9.24 ACE) to Corey Kluber at No. 4 is considerable: Kluber has a 7.97 ACE. After that are three pitchers headed the wrong direction because of recent performance and/or durability: David Price, Johnny Cueto and Madison Bumgarner.
3. Wait, Cueto is up that high?
The system is designed to weigh recent performance more heavily but not to overreact to it. It's similar in that way to the starting pitcher ratings based on Bill James' formula. In other words, the system thinks that going forward, Cueto will remain the solid Tier 2 starter that his track record suggests that he is, and that is also true for Price and Bumgarner, who is nonetheless dinged in the ACE system because of a drop in durability absorbed as a result of his first-half injury.
4. OK, so who is that guy who improved more than Sale and Scherzer?
That would be Detroit's Michael Fulmer. Fulmer's ACE score has jumped from 2.01 to 4.21, easily the biggest increase for anyone who entered the season in one of the top three tiers. In fact, he has jumped a tier, going from Tier 3 to Tier 2. Fulmer ranks No. 20 among the 262 starters rated for the study.
5. Any other tier jumpers?
Moving up or down a tier isn't that easy given the multiyear data being used here, but it happens. Beyond Sale, Scherzer and Fulmer, here's one guy who has moved from Tier 3 to 2 that might shock you: San Francisco's Jeff Samardzija. Samardzija may be the hard-luck hurler of the first half. He's 4-10 with a 4.81 ERA, which seems pretty awful. But he has struck out 127 and walked just 14, which translates to a fielding-independent ERA of 3.44. His numbers in walk rate and strikeout-to-walk ratio both lead the National League.
Other tier hoppers:
From Tier 3 to 2: Carlos Carrasco, Yu Darvish
From Tier 4 to 3: Sean Manaea, Aaron Nola, Tyler Chatwood, Jason Vargas, James Paxton
From Tier 5 to 4: Luis Severino, Ariel Miranda, Jeff Hoffman, Dylan Bundy, Patrick Corbin
6. What about the tumblers?
Three starters have slipped from Tier 2 to Tier 3, which you could argue is the most career-damaging tumble a pitcher can make. He's ostensibly going from a top-of-the-rotation stalwart to a mid-rotation guy, and there are a lot more of the latter across the population of MLB starters. The unfortunate trio: Jose Quintana, Adam Wainwright and John Lackey.
7. Does ACE capture the Cubs' rotation struggles?
You can be the judge here, but it's not a pretty picture:
8. Does ACE capture the Diamondbacks' surprising rotation breakout?
It certainly captures the unexpected degree to which Arizona's starter have performed so far. There was too much of a poor-to-mediocre track record entering 2017 to completely turn around their ACE ratings. That's not to say Robbie Ray, Taijuan Walker & Co. have been flukes -- it has just been an abrupt uptick for most the unit -- and they are headed in the right direction.
9. Is it even possible to move more than one tier in a half season?
Only one pitcher moved two tiers based on first-half performance, and he fits the mold of the only kind of pitcher that could do so. That is, he had some big-league track record entering the campaign (14 starts), but not a very long one. Thus, it has been a great first half for Minnesota's Jose Berrios, who has jumped from Tier 4 to Tier 2.
9. What about newbies?
Also known as rookies, there are a number of new players being rated who had not appeared prior to the start of the 2017 season. Here are the best of those, using a six-start minimum:
9. Who is bringing up the rear?
You hate to go negative, but for every leader, there is a laggard. Here are the bottom 10 ACE scores, again using the six-start minimum:
Who are the category leaders?
As mentioned, ACE scores are built on ratings in four overarching traits: performance, dominance, consistency and durability. Here are the current leaders in each of those categories. You will find the names are familiar:
Performance: Clayton Kershaw
Dominance: Clayton Kershaw
Consistency: Clayton Kershaw
Durability: Max Scherzer