Saturday, May 19, 2018

Pine tar or not: the Astros rotation has been frikking awesome

For the Astros, the season is (at the time of writing) 45 games old - just more than quarter of the season.  They have stuck rigorously to a five-man rotation - part of an incredible run of stability that has only seen three roster moves in seven weeks, none of which involved starting pitching - so the Astros starters have rotated nine times through the order.  Pretty much all of the starters have nine starts under their belt, except for that Verlander guy, who brutally stole a start from Charlie F. Morton possibly via some kind of mugging or armed holdup.

So this seems like a good time to review the season, with emphasis on the starting rotation...

A Quick Word on Stats and Imbalanced Schedules:
I am going to throw some stats around for y'all.  Some will be rate stats (stats on a per-game or per-inning basis) such as strikeouts per nine (K/9), which most of you will be familiar with.  Others will be counting stats, such as innings pitched, WAR and others - these stats tend to increase on a per game basis, so the more games, the higher the stat.  With this in mind, it is important to know that the Astros are pretty far-advanced in their seasons compared to some of their contemporaries.  At the time of writing the Astros (and a handful of other teams) have played 45 games, the most in baseball.  This is much more than another group of teams, including the Yankees, who have managed only 40 games.  This is partly due to the inevitable quirks in the schedule, and partly due to cancellations from a cold spring on the Eastern Seaboard and in the central US.  The Yankees sit on 40 games, as noted earlier, and are comparable to the Twins (39), the White Sox (40), the Mets (39), the Cardinals (41) and the Cubs (40).  So some of the counting stats may be a little misleading, especially when comparing the Astros to the Yankees, which many pundits have been doing a lot of this season already.

The Null Hypothesis:
The Astros rotation has been awesome.  Let's build the case...

The Basics:
Firstly, they have been incredibly healthy and durable, as mentioned before.  They have only used five starters.  Direct comparisons with other teams are prone to some bias of course.  For example, the Rays have been experimenting with a 4-man rotation and fifth bullpen day, so it really looks like they have used 8 starters but only four of them have started more than 5 games.  Other (more traditional) teams with vaunted starting rotations have used more pitchers: the Indians (7), Nationals (6), Dodgers (7), Red Sox (7), Yankees (6) and Cubs (6), all because of injuries or ineffectiveness.  I believe that the Astros are the only team to have only used five starters to this point of the season.  So the Astros have been both healthy, and metronomically consistent when allocating starts - something I thought was highly unlikely pre-season.

Secondly, the Astros starters have gone deep into games.  They lead the Major Leagues with 289 innings pitched, with the Indians second with 274 innings pitched.  The bottom of the table has the Mets at only 203.2 IP, but remember that IP is a counting stat, so the Mets have been disadvantaged to the tune of 6 games when compared to the Astros.  If you convert IP to a rate-stat (by dividing IP by the number of games played), the Astros actually get pipped by the Indians (6.4 versus 6.5 IP per game).  Also remember that the Indians bullpen has been famously horrible this season (5.68 ERA, worst in the Major Leagues), so the Indians may be a little more reluctant to pull their starters than other teams.

Comparing the Astros' 6.4 IP per start to other strong rotations: the Yankees manage 5.6 IP / start, the Red Sox check in at 5.8 IP / start and the Dodgers at 5.4 IP per start.  The Nationals, Cubs and Mets sit at 6.2, 5.3 and 5.2 IP/start respectively.  So only the Indians can match the Astros in this area.

Here is another shock - the Astros starters lead the Major Leagues in ERA in 2018.  By how much, you ask??  Have a guess.....  the answer is by over two-thirds of a run!!  The Astros check in at a 2.24 ERA, with the Nationals the next closest team (2.92).  Those are the only teams with a starting ERA under 3.  The Dodgers and Red Sox have far more expensive rotations*, and they check in at 3.48 and 3.63 respectively, while the Yankees have three starters earning minimum or close to it, and manage a very respectable 3.79 ERA.

* - How expensive, you ask???  Pro-rated, (i.e. the number of dollars divided by the number of contract years for the five main starters, added up) the Dodger's top 5 starting pitchers will cost just under 62MM while the Red Sox's will cost just north of 70MM.  In comparison, the Astros will spend 51.5MM on starters this year - which is a lot for them - but two of them will be off contract at the end of this year, and another two will be off contract at the end of 2019.  The Yankees rotation will cost just south of 40MM, which is a sign of just how good their front office has been at rebuilding on the fly.  Other rotations of interest: Cubs - 69MM, Nationals - 72.5MM.

Three True Outcomes:
Let's stick the the rate stats for now, and have a look at the strikeouts and walks.  The Astros lead baseball with a starting pitching strikeout rate of 10.7/9, a half K/9 higher than the Nationals (10.1/9).  The Dodgers are next (with a very symmetrical 9.9/9) followed by the Red Sox (9.8/9).  The Yankees (8.5/9) and Indians (8.4/9) both sit middle-of-the-pack (12th and 16th respectively).  The Astros' rate is within shouting distance of double that of the worst team in baseball (White Sox - 5.5/9)

The Astros sit third in starting pitching walk rate: 2.4 per 9.  They are bested by Cleveland (2.1/9) and Oakland (2.3/9), and are only marginally clear of the Dodgers and Nationals (both 2.6/9).  That could change with a bad Charlie Morton start, which is due to start shortly as I write this*.  Morton had a shocker in terms of walks in Arizona earlier in the year, so it isn't impossible.  But hey, being in a team ranked first in strikeouts and third in walks is going to result in a pretty solid K/BB ratio, which I will discuss next...

* - Update: Morton was awesome!! 1 walk versus 8 strikeouts over seven frames...

The Astros starters are unsurprising the best team in the baseball in K/BB ratio (4.22) over Cleveland (4.02) and Washington (3.92).  The Dodgers (3.88) and Red Sox (3.72) follow, with the Yankees (3.00) in eleventh.  I just want to mention the White Sox (aka the 2011-13 Astros), pointing out their K/BB rate of 1.16 is the worst in baseball.  By quite a margin.

Any readers getting this far down in the article are probably getting a little sick of being pummelled with stats at this time, so perhaps I will zip through the next few.  The Astros starters sit first in K-BB% (23.2), second in HR/9 (0.81), first in Batting Average Against (.186) and first in WHIP (0.94).  The Astros are first in ERA- (54, first by a massive 20 points) and FIP (2.30, leading by 0.3 of a run).  This is unsurprising, given FIP is calculated by the three true outcome stats, in which the Astros rank first, first and third (K/9, HR/9 and BB/9, respectively).  SIERA also ranks the Astros as the best rotation in baseball (3.10, over the Nationals, by 0.27 of a run).

Batted Ball Data:
Some of this could be attributed to luck, however, as the Astros starter also rank first / lowest in BABIP (0.250).  Some of that low-ness may be the result of shifting and the improvements in the Astros' overall defence this year, but that is probably optimistic outlook, in my opinion.  The BABIP seems destined to regress.  In addition to that, the Astros are second in baseball in ERA-FIP differential (-0.66), perhaps indicating that the rotation has not been as good as the three true outcome stats have predicted.

But perhaps much of this is sustainable, because the Astros also rank first in soft contact percentage (22.5%, besting the Red Sox by 0.5%), eighth in moderate contact percentage, and 29th in hard contact percentage.  Therefore, exit velocity data seem to support the idea that the Astros could continue to outperform their peripherals.  The line drive percentage allowed by Astros' starters is also the second-lowest in baseball (17.3%), while the Astros rank third in ground-ball percentage (46.8%).  So all of the basic batted ball data seem to indicate that the Astros' rotation outperforming its strong peripheral stats may not have been as much of a fluke as what could be thought at first glance.

The absolute dominance of the Astros starting rotation is really demonstrated by looking at Wins Above Replacement.  The caveat needs to be made that WAR is a counting stat and therefore disadvantages some teams (such as the Yankees, who don't really feature here).

In this category and according to Fangraphs*, the Astros possess a huge lead.  They sit on 8.4 fWAR, 1.4 times greater than the second-place Nationals (6.0).  Extrapolating the 2.4 fWAR difference between them over a full season (which is admittedly a very crude way calculating this projected difference), the Astros rotation is worth approximately 8.6 wins above the second place rotation in baseball - or nearly 1.75 wins per starter.  Scroll further down the list, and the interested reader will note that the Astros and Nationals are the only two teams with a starting pitcher WAR over 5.  The gap between first and third is huge - 3.5 wins above replacement.

* - Fangraphs calculates pitcher WAR by using FIP, so this result should not be surprising at all.

This WAR result is not just restricted to the fWAR, either.  bWAR* has the Astros as the first-ranked team of starters (5.5 bWAR), leading by 1.1 over the Red Sox (alternatively, 20% better than the Red Sox) and 1.6 over the surprisingly strong Phillies and unsurprising excellent Nationals rotations.  Combine this with the Astros' 8th ranked bullpen by bWAR and third-ranked position player bWAR, and you can see how the Astros have managed to be competitive this year, despite prolonged periods of offensive funkitude.

* - bWAR calculates pitcher WAR differently, combining pitchers runs allowed and defensive ratings to produce an ERA estimate, hence the difference in values.

A Quick Comparison to the 2005 Astros Rotation:
Remember that we are looking at the first 45 games of the 2018 season.  Probably the greatest Astros rotation this millennium was the 2005 team, who diehard fans will remember were 15-30 after 45 games.  But the 2005 team had a pretty good rotation (pitching was definitely the strength of that club!) - Roy O, Andy Pettitte and that Roger Clemens guy combined to form an very solid top three, with the last two spots being filled out by some combination of Brandon Backe, early career Wandy Rodriguez and the rookie Ezequiel Astacio.

That 2005 crew managed an overall ERA of 3.81 and accounted for 19.3 fWAR and 19.1bWAR over the course of the 2005 season.  The 2018 rotation looks like it would blow past those fWAR values, and exceed, to a much lesser extent, the 2005 bWAR value.  If one was to crudely multiply by 3.6 (100 divided by 27.8, the percentage of the season that has expired), then the 2018 Astros would be on course for a 30.2 fWAR and a 19.8 bWAR, which seems pretty excellent*.

* - more historical comparisons below...

Could it be the ball?
In summary, I think that there are two interesting features of the season to date, and they could well be interlinked.  The first (obvious) feature is the total dominance of the Astros starters, as outlined above.  Verlander is having the best season of his storied career, while Gerrit Cole is being compared to the Astros' part of Nolan Ryan's career.  Charlie F Morton has really earned that middle initial, which may stand for "filthy".  Dallas Keuchel has shown signs of putting it together lately after a rough start to the season.  Lance McCullers has managed a pretty strong season despite his filthy curveball not really consistently being there for him to this point.

I haven't mentioned the Astros offence at all since the start of this article.  The offensive woes are probably the reason the Astros aren't 34-11* at this point in the season.  In 2017, the Astros appeared to have a much more balanced offence - as a group of fans, we were left with the impression that they were solid from 1 to 9 in the order, and on any night, any part of the order could score enough runs to win the game by themselves.  This year, they have had a much more bimodal offence - there has been the solid top 4 (OPS's 0.770 or above include Springer, Altuve, Correa and Bregman) then an awful lower part of the order (OPS's below 0.650: Derek Fisher, Evan Gattis, Marwin Gonzalez and, of course, Jake Marisnick, all of whom have struggled for extended periods of time this year, despite playing fairly often).

* - In only 11 of 45 starts this year, Astros starters have allowed 3ER or more.  The breakdown: Verlander - 1; Cole, Morton and McCullers -  2 each; Keuchel - 4.

This makes me wonder about the ball.  While there are some reasons that Cole and Verlander may be better than they have ever been (health, data, pitching coaches to name a few), there was a lot of talk about the balls used during the World Series, and how their seams appeared less raised and therefore harder to grip.  This year, offence across baseball has dropped considerably compared to last year*.  The Astros team appears to exemplify this in and of themselves - their really good hitters with a decent track record are still really good, but the lesser offensive performers in the group just behind them (some of whom had career years in 2017) appeared to have regressed more toward their career rates.

* - 2018 Major League batting: .246/.318/.406; .160 isolated slugging; 1460 HR in 49281 PA's, or 1 HR every 33.8 PA's.  
2017 Major League batting: .255/.324/.426; .171 isolated slugging; 6105 HR in 185295 PA's, or 1 HR every 30.3 PA's

So is it possible that the two things are linked??  Could the same thing that has made the Astros rotation a juggernaut also be neutering some of the less able hitters in the Astros lineup??  The Astros are still really good, but it seems that this year, the Astros are really good in a much different way that they were last year.  This year, it is possible that speed, baserunning and small-ball will start to replace power as the Astros' main offensive determinant on things continue how they have currently been going.

Last Point:
The top single starting pitching season since 1962 - the first season of what has become the Astros franchise - as measured by fWAR was recorded equally by the 1970 Cubs and the 2011 Phillies.  Those teams were both ranked as having 26.0 WAR attributed to their starting pitchers.  Just within the Astros franchise, the top Astros rotation  was on the 1999 team, who managed a 21.7 fWAR.  This rotation was followed by the 1971 Astros starters, who recorded 19.6 fWAR.

So this Astros starting five could well be set to make history - both Astros history and Baseball history - if things continue the way they are currently going.  Logical reasoning says things won't go this well for the rest of the season, but there are some indications (such as the basic batted ball data) that the Astros' 2018 rotation could still be historic.  Taking their current fWAR of 8.4 and extrapolating that over a whole season would lead to an overall projection of 30.2 fWAR.  This would better the best rotation in recent baseball history by around 0.85 fWAR per starter, which is a massive difference.

For this reason, it is going to be interesting how the rest of the season pans out.  And if everyone stays healthy, it will also be fun to watch...

I hope this has been fun and informative.  Thanks, as always, for reading Astros County dot com.