Entering the season, there were legitimate concerns about the Astros’ bullpen. Yes, the club signed Josh Hader to form what was viewed, at least at the time, as a formidable backend of a bullpen consisting of him, Ryan Pressly, and Bryan Abreu. Formidable it hasn’t been. But there is still time for that trio to rebound following a rough start to the season (5.20 ERA in 45 innings). The middle relief options, however, were increasingly limited. Héctor Neris, Phil Maton, and Ryne Stanek threw a combined 185 innings in 2023, and all departed for new clubs in the offseason. While Hader essentially replaced Neris in terms of innings pitched, Dana Brown was looking internally and scouring the waiver wire to fill the openings of Maton and Stanek.
In turn, Rafael Montero’s role in 2024 was all but certain. While his performance last season was decidedly not good (5.08 ERA/4.46 FIP in 67 1⁄3 innings), the veteran’s $11.5 million in AAV and the sheer number of openings virtually guaranteed him a spot in the bullpen. A highly visible role, to boot. He would have to pitch himself out of a job, much like he did earlier last season before a muted improvement later in the summer. While a repeat of what was likely a career-best season in 2022 isn’t likely to be repeated, there were indications within his profile that Montero could generate better results. Some could point to his elevated .358 BABIP as a reason behind optimism, especially if that number could regress closer to his 2022 self. Strikeouts and whiffs were still up and his velocity was only down around 0.5 MPH. Home runs were a problem, but perhaps it was only a one-year kind of blip. Again, his actual results and peripherals weren’t optimal in 2023, but there was a justification for some optimism.
At first glance, Montero’s results this season haven’t warranted a demotion in job responsibilities. Considering how poor the backend of the bullpen has pitched to start the season, the right-hander’s 3.78 ERA looks appealing. I mean, he has done his job and helped keep opposing teams from scoring in the majority of his appearances. But there is a reason why we caution how to view ERA, as it can be misleading. I’d argue, in Montero’s case this season, increasingly misleading. First, let’s look at a disturbing trend for any pitcher: A sudden decrease in whiffs and subsequently in strikeouts.
First, a whiff rate chart.
Now a strikeout rate chart.
To see a whiff rate, which is strongly correlated with strikeout rate, decrease from 29.9% in 2023 to 18.8% this season is cause enough for alarm. For a pitcher, their strikeout rate tends to start stabilizing around 70 batters faced, or 17 1⁄3 innings. Montero is nearly there, with 65 batters faced and 16 2⁄3 innings on the season. In other words, the alarm bells are starting to register, at least for me. For reference, Montero finished 2022 with a 27% strikeout rate and 2023 with a 26.5% rate. Walks weren’t dramatically higher in either of those seasons and his walk rate now (7.7%) is lower than in the previous two years. But even accounting for strikeout rates that are just now starting to stabilize, a decline from 26.5% last season to 12.3% this season remains worrisome. In addition, Montero has also seen his called strike rate continuing to decrease at a notable clip, dropping from 17.6% in 2022 to 12.7% in 2024.
So, what has changed? From a pitch movement standpoint of his primary three pitches — four-seam, changeup, and sinker — between last season and this one, there is a little change to take into account. There is a difference in how these pitches break horizontally and vertically, but usually within an inch or so. Not enough of a change in most cases to confidently point to that aspect as the primary reason for his underlying performance issues. Incidentally, Montero’s slider has exhibited more change in its overall break, but he has only thrown 15 sliders this season.
From a location standpoint, Montero’s four-seam has had the occasional issue bleeding into the middle of the zone at times. But that isn’t an abnormal development for the right-hander, as that issue has been present for a while. A somewhat expected problem for a pitcher who embraced throwing his four-seam higher in the zone; occasionally, one of those will end up lower in the zone than called for. It does appear that he is missing too high a bit too often though, leading to his four-seam landing outside of the zone more than intended. The other pitch leading to a higher rate of pitches thrown outside the strike zone is his changeup. That would explain, at least partially, the lowered zone and called strike rates we’re seeing now. On the plus side, however, his four-seam is bleeding into the edges — roughly 50% — at roughly the same rate as in 2022, when Montero was at his best.
But location by itself doesn’t explain the heart of the problem, although it does shine some light. Ironically, Location+, a component of the Stuff+ pitching model, actually thinks Montero’s location has improved compared to past seasons. Rather, it lies within how poorly his stuff has deteriorated since 2022.
Stuff+, since 2022
2022: 115
2023: 106
2024: 97
Of the three pitches Montero utilizes the most, only his changeup has seen a rebound in Stuff+ this season, increasing from a rating of 74 to 101, but still a far cry from his 121 mark back in 2022. His four-seam and sinker have notably struggled compared to past seasons, with both being reflected in a 97 rating. It is worth noting that Montero’s average velocity has suffered across the board, with his four-seam now measuring about 1 to 1.5 MPH less on average compared to his previous seasons as an Astro.
In addition, Montero’s fastball is less flat as it approaches this season (0.82 degrees VAA AA) compared to past seasons (0.87 degrees VAA AA). Velocity, pitch movement, and spin rate can impact how the ball approaches the plate. For Montero, we’ve seen his velocity decrease and pitch movement changes remain relatively minor. The spin rate, however, has increased for all of his pitches. There is also the release point to consider and that aspect of Montero’s performance has adjusted since 2022 on both the horizontal and vertical planes, at least on four-seam fastballs. These changes could also explain part of the ongoing issues.
Opposing hitters haven’t had that much success against Montero thus far, but the expected numbers indicate that could change. Combining all pitch types, opposing hitters have a .207 batting average and a .431 SLG along with a .320 wOBA against Montero. However, when accounting for the expected metrics, all three categories jump to .261, .442, and .342, respectively. An increase in groundballs has assisted in keeping any batted ball damage limited, which is also evident by the .191 BABIP. That’s a good thing so far as home runs continue to be a thorn in the right-hander’s side, already allowing three. For reference, he only allowed three dingers in 2022 followed up by 11 in 2023. Barrels also remain elevated, which is in line with last season, but unfortunately not with 2022.
Plenty of indicators point to Montero’s results progressively worsening over time, especially if his velocity and whiffs remain down compared to past seasons. Part of his resurgence in 2022 was due to his ability to utilize his four-seam with its velocity higher in the zone to great effect. With opposing hitters becoming more adept at handing those higher fastballs in addition to any diminished stuff, it could lead to poorer results for pitchers, as we’ve already seen. In turn, I’d advise that we shouldn’t be surprised if Montero’s actual results take a turn south in the coming weeks and months. Considering the context of the season up to now, and the fact that he counts $11.5 million in AAV for this season and next, it isn’t a great development. It is also a cautionary tale for clubs why re-signing relievers is a minefield compared to other positions.