The Bullpen Has Been Excellent So Far
Astro Relievers Have Increased Their Use of 4-Seam Fastballs in 2022. It Has Let to Fewer Walks and Fewer Runs Allowed. Will That Continue?
What a difference a year makes.
Last season, the Astros bullpen was a source of great consternation among Astros fans. And, based on how the bullpen performed, that agita was well earned.
I had takes on the bullpen that were more optimistic than the average Astros fan, which kept saying the Astros as a team and individually were average in the bullpen. The bullpen was of course the center of the front office’s focus at the trade deadline, as they acquired Kendall Graveman, Yimi Garcia, and Phil Maton in an effort to shore up the bullpen.
This year, the bullpen has been a completely different story. The chart below tells the story. The Astros bullpen has the lowest ERA in the majors at 2.62. Of course, part of the Astros ability to prevent runs is having one of the best defenses—if not the best defense—in the majors. But the FIP for the Astros bullpen is quite solid at 3.31, 4th in the majors.
The numbers show that Astros relievers are forcing opposing hitters to hit the ball into the teeth of the Astros defense, with great success. The Astros bullpen are striking out relatively few batters (8.8 per nine innings, 19th best in MLB), but are not walking batters (3.1 per nine, 4th best). Astro relievers, in combination with the defense, are holding down base hits from the opposition, who have a collective .210 batting average against Astro relievers. In short, Astro relievers are keeping opponents from getting to first base.
The next chart shows the basic numbers for the seven relievers who have thrown the most innings for the Astros.1 It leads me to a couple of observations. First, Dusty Baker and pitching coach Josh Miller have been able to spread out the bullpen innings across a number of relievers. No one (or two) relievers has taken a disproportionate share of innings.
Second, the quality of the bullpen is also spread out over a number of pitchers. Two relievers (Montero and Stanek) have ERAs under 2.00; another two (Neris & Pressly) have ERAs in the 2’s; another two (Abreu and Maton) have ERAs in the 3s, and only Blake Taylor has an ERA over 4.00. So while relievers like Maton and Taylor have raised my blood pressure while on the mound, no major Astro reliever has been an abject disaster in 2022.
Third, the pattern of having an ERA lower than a FIP is shared across the bullpen—only Bryan Abreu has an FIP lower than his ERA. And fourth, the biggest contributions to the success of the Astros bullpen this season have been made by Hector Neris, signed this off-season as a free agent, and Rafael Montero, who was acquired seemingly as a throw-in in the Kendall Graveman-Abraham Toro deal.
More Fastballs.
So what has been different for the Astros bullpen this season? One trend that has been notable—and something that we have been tracking on my show Astros Orbit in Twitter Space with Cody Poage (@astro_numbers) of The Crawfish Boxes—is the increased use of the 4-seam fastballs by Astros relievers. The box below shows the Statcast charts for pitch usage for (clockwise from top left) Hector Neris, Rafael Montero, Ryne Stanek, and Ryan Pressly). Each of these pitchers has increased the use of his 4-seam fastball (it’s the dark red line in each chart).
The increase is sharpest for Montero (who increased his fastball usage from 35% in 2021 to 55% of all pitches this year ) and Neris (whose increase goes from 37% in 2021 to 50% this season). The increases for Stanek and Pressly are more gradual, but still clear in the charts. Each of these four pitches is throwing his 4-seam fastball more than any other pitch.
There are a couple of things worth noting about this increase in fastball usage. The first is that it goes against some of the recent trends in pitching, in which pitchers have reduced fastball usage while throwing their “best pitch” more frequently; with that best pitch usually being a breaking ball. And the team that pioneered this effort is our Astros, under former pitching coach Brent Strom. But batters constantly adjust to the changes in pitching strategies and this pitchers have to adjust back. Throwing more fastballs seems to be an adjustment made by Astros relievers to the shifts in hitting strategy.
It also may be an adjustment to the new ball being used this season, which is travelling less than in previous seasons. This has reduced homers in particular, but hits of all kinds (doubles are significantly down too). Throwing more fastballs and daring hitters to do something with it is a more viable strategy if the ball is less likely to carry over the fence.
And that strategy is working so far this season. Neris gave up a slugging percentage of .421 on 4-seam fastballs in 2021; this year, that same pitch has produced an opponent’s slugging percentage of .333. Stanek has dropped his opponents’ slugging percentage on his 4-seam fastball from .389 in 2021 to .219 this year; the slugging percentage against Pressly’s heater has dropped from .372 to .278. And the biggest drop is from Montero’s 4-seam fastball. In 2021, opponents slugged .405 against that pitch; this year, it’s .158.
Daring Opponents’ to Hit Their Fastballs
The increased fastball rates have had other effects in the data. It is an easier pitch to throw for strikes than a breaking pitch, and Astro relievers have dropped their walk rate from 4.01 per 9 innings in 2021 (20th best in the majors) to 3.09 per nine this year (4th best in MLB).
But the reliance on the fastball has also changed the type of strikes that Astros relievers are getting. They are 3rd in the majors in their share of swinging strikes at 13.6%. In short, they are getting a lot of swings and misses. But they are last in the majors in the percentage of called strikes that they are getting. In fact, they are only getting called strikes on 13.5% of their pitches—that’s a lower share than their rate of swinging strikes.
By throwing fastballs in the zone, Astro relievers are daring opponents to hit balls. And opponents are trying; Astros relievers have induced the highest rate of swings of any major league bullpen at 75.0%. And yet, opposing batters are not making contact. Opponents are making contact on only 81.1% of those swings at balls in the strike zone—the second lowest rate in the majors.
There is of course risk in the fastball heavy strategy that Astro relievers are employing. Hitters are known to “hunt fastballs” because they find it easier to hit balls thrown mostly straight than those designed to bend sharply on their way to the plate. So far, Astros relievers have given up only 10 home runs in the 151.1 innings they have pitched this season. That’s the lowest number of homers of any bullpen. The bullpen has allowed home runs on only 6.2% of the flyballs they have allowed, the 2nd lowest rate in the majors.
So far, the fastball heavy strategy has produced solid results for the Astros bullpen. They have significantly cut their walk rates while, in conjunction with the team’s excellent defense, limiting base hits and home runs. This combination has proved very effective so far. We will see if it continues all season.
Other relievers have thrown 29.1 innings this season for the Astros. Cristian Javier threw 8.1 innings as a multi-inning reliever before he entered the starting rotation. The combination of Seth Martinez, Ronel Blanco, Parker Mushinski, and Pedro Baez have thrown for a combined 21.0 innings.