Two days before Opening Day, the Diamondbacks made one of the bigger free-agent splashes in franchise history by signing left-handed starter Jordan Montgomery.

Montgomery, 31, was coming off arguably the best season of his career. In 188.2 innings with the St. Louis Cardinals and Texas Rangers in 2023, he logged a 3.20 ERA, 1.19 WHIP and 166 strikeouts to 48 walks. It was his third straight year making 30 or more starts with a sub-4.00 ERA.

The Diamondbacks landed one of the top starters on the market for a fraction of the total guarantee that he was expected to receive.

Two months later, suffice it to say the move has not gone as planned.

On Wednesday, Montgomery walked off the Chase Field mound to a chorus of boos after allowing six runs in two-plus innings against the San Francisco Giants. The outing brought his season ERA to 6.80.

“Another stinker,” Montgomery said.

Among major leaguers with 40 or more innings pitched this year, Montgomery has the highest ERA in baseball.

After his outing against the Miami Marlins on May 25, Montgomery acknowledged that missing spring training played a role in his early-season struggles.

Did it impact his start on Wednesday, too?

“No,” Montgomery said. “I just stink.”

There are probably many factors in Montgomery’s slow start with the Diamondbacks. We’ll present a handful of ideas here, beginning with the most obvious: that Montgomery’s fastball velocity is as low as it has been in five years.

Jordan Montgomery’s Diminished fastball velocity

After averaging a career-high 93.3 mph with his sinker in 2023, Montgomery has averaged 91.6 mph on the pitch this year, his lowest mark since 2019.

Last year, Montgomery threw his sinker nearly half the time. By Baseball Savant’s run value metric, it graded out as the fifth-most valuable sinker in all of baseball.

In 2024, the results have been quite different:

Of course, there is more to a pitch than its velocity. Movement is also a factor. However, Montgomery’s sinker has seen almost no change in movement this year. Velocity is the obvious separator here.

When asked about Montgomery’s dip in velocity after Wednesday’s game, Lovullo said that he was not concerned.

“It’s just about putting it where he wants to,” Lovullo said. “If he’s 91-92, I’m perfectly fine with that as long as he’s placing it in the right spot.”

Looking at Montgomery’s sinker pitch chart from Wednesday’s game, it is not hard to pick out a few location mistakes:

Nonetheless, it is worth noting that Montgomery’s sinker location this year does not appear to be all that different from recent years.

In 2024, Montgomery has thrown 32.8 percent of his sinkers in the heart of the plate compared to 29.3 percent last year and 31.6 percent the year prior. The difference there is noticeable, but not alarming.

Montgomery’s percentage of sinkers in the shadow zone — which covers the area at and around the edges of the strike zone — is actually a touch higher in 2024 than in each of the past two years. Hitters have done considerably more damage on those pitches this season, however, with a .313 batting average in 2024 compared to .228 in 2023 and .221 in 2022.

And that brings us back to where we started: Montgomery’s sinker velocity is down, and the pitch seems to be more hittable as a result.

Montgomery was asked about the impact of that velocity drop after his outing on Wednesday.

“Definitely been searching for it,” he said. “I’m stronger than I’ve ever been. I don’t really know what it is. Just hasn’t clicked yet.”

Where did the strikeouts go?

While Montgomery has never been known as a power arm, strikeouts have been dangerously rare for him in 2024. Out of 172 pitchers who have thrown 500 or more pitches this season, Montgomery’s 13.4 percent strikeout rate is the sixth-lowest mark in the majors. Last year, Montgomery’s strikeout rate was 21.4 percent, which was around the league average.

The explanation for that issue has less to do with Montgomery’s sinker than his two main secondary pitches: the curveball and changeup.

Montgomery has thrown his curveball 30.9 percent of the time this year, his highest rate since 2019. It’s been his best pitch in 2024, but the results still pale in comparison to last year:

Oddly enough, opposing hitters are actually doing less damage against Montgomery curveballs that are in the strike zone this year. Curveballs out of the zone are a different story. Opposing hitters are chasing out-of-zone Montgomery curveballs at a comparable rate to past years, but they are whiffing less and putting the ball in play more.

Remarkably, opposing hitters are batting .273 (6-for-22) this year on Montgomery curveballs that are out of the strike zone. Compare that to a .128 average (10-for-78) on such pitches last year, and an .039 average (3-for-76) the year prior.

Here is a particularly extreme example, in which Detroit Tigers shortstop Javier Baez digs out a Montgomery curveball that is well below the zone:

So, why is Montgomery’s curveball more hittable this year? As with the sinker, one possible explanation is velocity.

This year, Montgomery’s curveball is averaging 78.8 mph, down from 80.5 mph last year. After his start against the Marlins on May 25, Montgomery said that his curveball is typically at its best when it lands in the 79-81 mph range. The numbers bear that out.

Since the start of the 2022 season, Montgomery’s curveball has performed much better in the 79-81 mph range than the 77-79 mph range:

The slugging percentages are comparable, but the whiff rates are strikingly different.

It is worth noting that, while Montgomery has had past success with a sinker that averaged under 92 mph — see his rookie year in 2017 with the New York Yankees — his curveball velocity has never dipped this low in his big-league career. In that sense, he is in uncharted territory.

Now, on to Montgomery’s changeup. Frankly, it has gotten hammered:

Again, it is tricky to pin down exactly why that is. Montgomery’s changeup movement is effectively the same as it was last year, and his velocity on the pitch is down, but only by 0.7 mph. The most clearly identifiable issue appears to be pitch execution.

As shown in the following heatmaps, Montgomery did a nice job of controlling the arm-side edge of the zone (outside corner to righties, inside corner to lefties) with his changeup in 2023. His chart this year is more sporadic:

Last year, Montgomery threw 25.5 percent of his changeups in the shadow or chase zones on that arm-side edge, where the pitch figures to be most effective. This year, that number is just 15.9 percent.

While Montgomery’s 33.3 percent whiff rate on the changeup is still above the league average, his putaway percentage on the offering is just 7.7 percent this year. Last year, that figure was 20.8 percent. In other words, Montgomery has been able to induce whiffs on the changeup early in counts, but he has struggled to finish hitters off with it.

Over the past few weeks, Montgomery’s changeup usage has trended downward. After throwing it 23 percent of the time last year, he has thrown only 15 of them in his past two starts combined.

Silver linings

There is no sugarcoating how poorly Montgomery has started for the Diamondbacks. This nine-start span is the worst of his career. But a couple of positive final points are worth making.

First, as alluded to previously, Montgomery had success in 2017 in spite of a sinker that averaged only 91.7 mph. That year, he had a 3.88 ERA with the Yankees in 155.1 innings.

Opposing batters hit the sinker hard that year (.342 AVG, .550 SLG), but Montgomery threw it much less than he has in recent years, and his changeup and curveball were good enough to make him effective. He might need to take a similar course of action this year, provided that he can get those secondaries back on track.

Second, while Montgomery’s command has been subpar this year, he has long been one of the better pitchers in the league in that regard. Even if Montgomery’s stuff does not return to last year’s levels, he could be a simple mechanical adjustment or two away from hitting his spots consistently again.

That might not make Montgomery a frontline starter, but it could make him an effective innings-eater. And with three-fifths of the starting rotation on the injured list, that is something the Diamondbacks sorely need.

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Top photo: Rob Schumacher/The Republic