What's Wrong With the Houston Astros' Pitching Staff?

The Houston Astros are in last place in the American League West, are tied for 25th in average margin of victory, and have allowed the fifth-most runs per game in MLB.

It’s April 21, so there is probably good reason not to panic about this. Then again, Houston’s 5-10 record, combined with solid starts in Oakland and Texas, have taken a very real hit on the Astros’ playoff odds.

We give Houston a 26.0% chance to make the postseason, and this marks a 25.6% drop from their playoff probability on Opening Day (the largest drop of any team in MLB). This does seem harsh after just 15 games, but Houston’s playoff odds also dropped by 20.4% at FanGraphs, so it's not like we're alone.

The Astros are tied for the fourth-highest wRC+ (119) in the Majors, but are 23rd (with a wRC+ of 82) with men on base, dropping them to a tie for 19th in runs scored per game. Sequencing, though, does not seem to be a true skill for teams, so if Houston’s hitters continue to produce like they have, the runs will come.

The bigger problem has been in terms of run prevention, where the Astros are 27th in ERA (4.81) and 26th in FIP (4.55). Things look even worse after park adjustments, as they are last in ERA- (132).

Some of this can be explained by an unsustainably high home run per fly ball rate (17.2%), but there have been more to their struggles than this.

Where Have the Strikeouts and Grounders Gone?

Last season, Houston’s starting rotation was the eighth-most valuable in the Majors (in terms of fWAR), and rode a Top-12 strikeout rate (19.9%), Top-10 walk rate (7.0%), and Top-4 grounder rate (48.3%) to finish with a 92 ERA-, 93 FIP- and 94 xFIP-.

This season, the Astros’ starters own a 132 ERA-, 122 FIP- and 110 xFIP-. 

What happened?

The staff’s walk rate is a solid 7.2% (tied for ninth in MLB), but its strikeout rate has plummeted to 16.2% (29th) alongside its grounder rate (44.0%, 22nd).

They have not been helped by that home run per fly-ball rate, a .309 BABIP, or 70.7% Strand Rate, but it is still much too early to worry about these numbers, as all are especially prone to random variation, and should regress towards the mean going forward.

Frankly, the walk, strikeout, and grounder rates could regress as well, but these three stats are relatively stable, so if something is truly wrong with Houston’s pitching, we’d see it in these numbers first.

Even staff ace and reigning AL Cy Young winner Dallas Keuchel has not been immune to this apparent slump, though you would not know it by just looking at his shiny 2.18 ERA or even his 3.00 FIP.

He has been the beneficiary a low .250 BABIP, but, in his case, this may very will be partly reflective of an actual skill rather than good fortune or randomness.

Keuchel’s peripherals though, have been mediocre so far. His strikeout rate has dropped to 20.2% from 23.7% last year, and has been accompanied by a decline in swinging strike rate. The again, he had never been a big strikeout pitcher prior to last year and has a career average of 18.9%, so perhaps this drop-off is not quite so stunning.

The drop in walks (and to a lesser extent, grounders), though, has been truly perplexing, as his walk and groundball rates of 13.1% and 56.4% are below his career averages of 7.0% and 59.3%, respectively.

Last season, Keuchel managed a 5.6% walk rate and 56.4% groundball rate, making his declines in both areas even more confusing (his pitch usage has been almost identical this season relative to 2015).

He has yet to be truly burned here thanks to the fact that none of his fly balls have actually left the park. Given what we know about the volatility of HR/FB% and the fact that Keuchel’s career rate is 13.7%, it would not be wise to expect this continue, and this explains why his xFIP of 100 is 14 points worse than his career average.

Collin McHugh, who was a 3.9 fWAR player last season, has seen his strikeout rate (17.5%) decline for the second straight season. While his walk rate (4.8%) is good, his 35.4% groundball rate will make him dependent on HR/FB% suppression, and though it hasn’t bit him yet, we should expect his 4.3% HR/FB rate to regress.

Unlike Keuchel and McHugh, Doug Fister, Scott Feldman and Mike Fiers have all had rotten home run luck, as all of three have allowed a 17.6% HR/FB rate or worse. This has been especially harmful, since they have allowed groundball rates of only 39.7%, 41.2%, and 37.3%, respectively.

With the possible exception of Fiers (who has a team-high 14.1% K-BB% and 93 xFIP-), expected home run rate regression will not be enough to save this group if they continue pitching like they have; Fister is only striking out 12.7% of the batters he’s faced, while Feldman has a 14.3% strikeout rate and 10.0% walk rate.

As for Houston’s bullpen, the results have been equally poor, but at least the process has been better. The Astros are 25th in bullpen ERA and 22nd in bullpen FIP, but this is almost solely due to an insane 20.8% home run per fly ball rate.

The Houston bullpen is sixth in strikeout rate (27.9%) and 13th in walk rate (7.5%), helping them rank third in K-BB% and fourth in xFIP (3.15).

Going forward, the Astros should get a boost from the return of Lance McCullers, who was a 2.8 fWAR pitcher last season, and could return in May, according to MLB.com.

This would surely be a shot in the arm, and it’s also not all that difficult to envision improvement from his fellow starters who had strong seasons last year.

For the Astro’s sake, this will need to start happening soon, because, crazy as it sounds to say in April, they are losing ground in the hunt for October.