Exploring An Astros Pitching Question

This article will explore a topic pertaining to the Astros’ starting pitchers, with a particular focus on Framber Valdez and Hunter Brown. But, as a preface, I will update the Astros’ current pitcher rankings.

ASTROS’ RANKING

The overall pitching staff ranks 5th in ERA (3.81) and 17th in FIP (4.26). The Astros rank 11th in SIERA (4.11), which is an advanced pitching metric that tends to be more predictive. The Astros pitch rankings have declined since the early part of the year when the Astros frequently occupied the 1st or 2d rank in ERA. The Astros have accumulated a league-leading 50 unearned runs, which could mean that RA/9 is a more incisive measure of run prevention. The Astros’ pitchers are ranked 7th in RA/9 (4.19), compared to ranking 5th in ERA.

The Astros’ pitching staff has the largest gap between ERA and FIP in the majors. FIP is “fielding independent” and therefore ignores the team’s ability to field balls in play. The size of the gap between ERA and FIP could reflect the quality of the Astros’ defense. Given that the Astros’ defensive metrics have declined this season, it’s also possible that the FIP is indicating potential for future regression by the Astros’ pitchers.

One could view SIERA as a middle ground between ERA and FIP, inasmuch as it reflects interactive pitching skills that affect both strikeouts and walks, as well as the ability to affect some elements of run prevention after contact. The Astros’ bullpen ranks 7th among relievers in SIERA (3.72). The Astros’ rotation has a more troubling 16th in SIERA (4.12).

SHOULD WE BE CONCERNED ABOUT THE RATE OF HARD-HIT BALLS ALLOWED BY FRAMBER VALDEZ AND HUNTER BROWN?

Among qualified major league starters, Framber Valdez allows the highest exit velocity, and Hunter Brown allows the eighth-highest exit velocity. (Fangraphs leaderboard) As I noted in a previous article, the ability of a pitcher to control hitters’ exit velocity is up for debate. But it is intuitive that some aspects of a pitcher’s skill (e.g., pitch location, pitch movement) probably can affect exit velocity.

Among the Astros pitchers who have pitched in the rotation this year, 46% of the variation in ERA can be explained by exit velocity. Although the sample is small for this R-square test, the result does suggest that exit velocity affects the pitcher results. In my previous article on this subject, I discussed the possibility that Valdez’s and Brown’s ground ball percent may mediate the potential damage from high exit velocity, by limiting extra-base hits.

Some other observations based on researching this question:

• Exit velocity explains about 18% of Valdez’s game-to-game ERA, but has only a marginal effect on Hunter Brown’s game-to-game ERA. It’s notable that Brown experienced a 1.1 mph increase in exit velocity since June 1. But, unlike Valdez, Brown has maintained a similar ground ball rate before and after June 1, which may moderate the impact.
• Framber Valdez’s game-to-game performance reflects a significant decrease in ground ball rate since March-May. Framber’s average ground ball rate per game is 48% since June 1. Prior to June 1, Valdez’s ground ball rate per game was 60%. The only ground ball rate higher than 60% since June 1 was Valdez’s no-hitter (63% ground ball rate).
• On a game-to-game basis, the ground ball rate explains about 14% of Valdez’s ERA and 29% of Brown’s ERA. This comparison is based on applying the R square statistic to the two pitchers’ game logs at Fangraphs.
• Over the last 28 days, Valdez has a 6.10 ERA (compared to the season ERA of 3.30). This elevated ERA is notable, considering that he pitched a no-hitter during that time frame. Also over the last 28 days, Valdez allowed a .466 SLG%, which s almost 100 points higher than his season average. During that same time frame, Valdez’s exit velocity (91.9 mph) and ground ball rate (47.25%) were both at an elevated level higher than his season average.
• Over the last 28 days, Hunter Brown has also experienced a significant uptick in his ERA (4.60) and SLG% (.566—more than 100 points higher than the season average).
• Some Astros’ starters have exhibited an ability to suppress exit velocity so far this season. Ronel Blanco, J.P. France, and Jose Urquidy have produced average exit velocities below 89 mph.

My conclusions:

• The high exit velocity allowed by Framber Valdez and Hunter Brown is cause for concern, but not panic. It is not unusual for Valdez to experience higher than average exit velocity, and exit velocity can be volatile during a season.
• Hunter Brown’s ground ball rate has been relatively consistent, but Valdez has exhibited a significant decline in his ground ball rate. It’s possible that an increased pitch velocity on Valdez’s sinker has some effect on a decreased ground ball rate, but I couldn’t detect a linkage in the data at this level.
• The ability of Brown and Valdez to locate pitches down in the zone, as well as the movement on their breaking pitches, will be of interest in the coming months.
• Other pitch characteristics, like first-pitch strikes, whiff rates, and the like, were not analyzed, but are important leading indicators of pitching performance.
• For ground ball pitchers like Brown and Valdez, the absence of infield shifts may increase the damage from high exit velocity. In any event, executing good infield defense will be important. The defensive metrics indicate that the Astros’ defense has declined relative to last season, which may account for some of the recent decline in pitching performance.

Valdez and Brown are superior pitching talents; let's see if they improve in the future.