How a promising Diamondbacks pitching staff turned in one of the most disappointing seasons in team history

Entering play on Sept. 22, the Diamondbacks were 87-68. They had won three straight games against the NL-Central-leading Milwaukee Brewers. With seven games to play, a projection system gave them a 93 percent chance to make the playoffs.

Then, in their series finale in Milwaukee, the Diamondbacks took an 8-0 lead in the third inning. At that point, the thought of them leaving town with anything other than a four-game sweep was basically unimaginable. Somehow, that thought became reality.

For the first time in franchise history, the Diamondbacks lost a game in which they led by eight runs. Eight days later, they could only watch on TV as the Braves and Mets split a doubleheader that spelled the end of their postseason hopes.

In retrospect, Diamondbacks manager Torey Lovullo believes that blowing that eight-run lead in Milwaukee had lingering effects.

“I think something happened to this team from that game,” Lovullo said in his exit interview last week. “That’s my gut feel.”

Looking back, it would be easy to chalk up the Diamondbacks’ downfall to a very bad finish, set up by perhaps the worst loss in franchise history. There is some truth to that narrative. But it is not a complete one.

The reality is that the Diamondbacks were flawed. Their pitching simply was not postseason caliber.

In 2024, Diamondbacks pitchers combined for a 4.62 ERA, the fourth-worst mark in baseball. They had a 91 ERA+, which means that they were nine percent below league average. The last time a team made the playoffs with an ERA+ of 91 or worse was 1981, when the Brewers and Philadelphia Phillies did it. The last team to even finish .500 or better with an ERA+ that low was the 2003 St. Louis Cardinals.

The fact that the 2024 Diamondbacks won 89 games is a testament to their exceptional offense. They led the league in runs, and it wasn’t close. But the shortcomings of this Diamondbacks still pitching staff proved too much to overcome.

Perhaps the biggest factor was a pair of free agent signings that could not have gone much worse than they did in the first year.

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Diamondbacks’ free agency spending gone wrong

After not having a fourth starting pitcher for the NLCS or World Series last year, Diamondbacks general manager Mike Hazen went into the offseason hellbent on not seeing that happen again.

So, the club signed two of the top free agent starters available last offseason in Eduardo Rodriguez and Jordan Montgomery. Combined with Zac Gallen, Merrill Kelly and Brandon Pfaadt — the same trio that helped the team reach the World Series last year — the Diamondbacks had the makings of one of the better rotations in baseball.

Instead, their starter ERA increased from 4.67 last year to 4.79 in 2024. The Chicago White Sox, a team that just posted the worst record in major-league history, had a better starting rotation than they did.

“I can’t really make sense of it right now,” Hazen said of the Diamondbacks’ pitching taking a step back. “The last month, I’ve tried to make sense of it in my mind.

“I feel like this was a veteran group of starting pitchers. We had some young kids take a few steps forward for sure. But I don’t know where it went sideways … Our pitching needed to be better.”

It wouldn’t be fair to pin the Diamondbacks’ starting pitching issues solely on Rodriguez and Montgomery, but neither had a strong year.

Rodriguez suffered a shoulder injury just days before the regular season that kept him out until early August. He wound up making just 10 starts, with a 5.04 ERA, 1.50 WHIP and 47 strikeouts to 19 walks in 50 innings.

Montgomery, meanwhile, signed with the Diamondbacks just before the season began. He missed spring training entirely, and he never seemed to find a rhythm.

In 25 games (21 starts), Montgomery had a 6.23 ERA, 1.65 WHIP and 83 strikeouts to 44 walks in 117 innings. He lost his starting rotation spot to Ryne Nelson in late August, but regained it in September when Nelson went on the IL.

Among pitchers who threw 100 or more innings in 2024, Montgomery had the highest ERA in baseball. He made $25 million in 2024, and is expected to exercise a $22.5 million player option for 2025.

Of the two, it is easier to overlook the struggles of Rodriguez. Fifty innings is hardly a conclusive sample for any pitcher, much less one returning from four months on the injured list. Rodriguez was pretty good in three of his final four outings, and his stuff was comparable to past years in terms of velocity and movement.

Montgomery, on the other hand, lost about 1.5 mph on all of his pitches, and his typically stellar command was absent for most of the year. Maybe he will look like his old self in 2025 after a normal spring training. The fact that he never showed much progress over the course of the 2024 season warrants concern, however.

Regardless of what the future holds, the reality is that the Diamondbacks signed two of the more highly respected starters available and essentially got replacement-level results in the first year. Rodriguez and Montgomery pitched in 35 games (31 starts) with a 5.87 ERA and an average of under five innings per start.

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Outsized impact of starting rotation injuries

If Eduardo Rodriguez had been the only Diamondbacks starter to miss time in 2024, they probably would have been fine. That was not the case.

In addition to Rodriguez, the Diamondbacks lost right-hander Merrill Kelly to a shoulder injury for four months. Ace Zac Gallen missed a little over a month with hamstring issues. Ryne Nelson, the team’s most consistent starter in the second half, had two separate IL stints that saw him miss 2-3 starts each.

Mike Hazen was adamant in his exit interview last week that those injuries should not be used as an excuse.

“Injuries are injuries,” Hazen said. “Every team is injured. Look at the number of pitching injuries the Dodgers have taken on in their rotation. They won the division.”

Excuse or not, the impact of those injuries appears to have been massive. Outside of the five starters that were on the Opening Day roster, the Diamondbacks wound up using eight other starting pitchers this year (three of whom were relievers acting as openers). That group logged a combined 33 starts with a subpar 5.48 ERA:

Name	GS	IP	ERA	WHIP	K%	BB%	BAA
Slade Cecconi	13	61	5.75	1.31	19.6	5	.279
Tommy Henry	7	32	6.47	1.69	17.4	8.7	.313
Yilber Diaz	4	20	4.05	1.30	16.9	9.6	.243
Blake Walston	2	9	2.00	1.22	15.4	12.8	.194
Scott McGough	2	3	6.00	1.00	25	8.3	.182
Brandon Hughes	2	1.2	0.00	1.20	28.6	0	.286
Joe Mantiply	2	1.2	5.40	0.60	0	0	.167
Cristian Mena	1	3	12.00	2.33	13.3	20	.333

Outside of Nelson, who took Rodriguez’s spot on the Opening Day roster, the Diamondbacks did not get consistent results from any of their other fill-in starting pitchers.

Organizational pitching depth has been an issue for a while. Developing quality starting pitching is easier said than done, but the Diamondbacks have had a particularly hard time with it. When pitcher injuries arise, their line of defense tends to be pretty weak. That was the case in 2024.

Of course, the impact of starting pitcher injuries goes beyond the period of time that those players miss. It can take time for those pitchers to find a rhythm when they return.

Kelly, in particular, did not look like himself after he first came off the injured list. He had a 6.75 ERA in his first four starts after returning. He then followed that up with a 3.58 ERA in his final five starts of the season.

Gallen said in September that his midseason hamstring injury happened at a particularly bad time, just as he was starting to find a rhythm.

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What underlying metrics say about Diamondbacks pitchers

In a conversation with PHNX Sports in mid-September, former Diamondbacks pitching coach Brent Strom — who was reportedly fired last week — spoke about some of the trends that were causing his pitchers to struggle.

“We’re very good in some categories and not very good in others,” Strom said. “We get ahead in the count. We throw first-pitch strikes. We have not done a very good job of evacuating the zone when we’re ahead in the count. We haven’t done a very good job of just being more efficient with our pitches.”

As Strom pointed out, the Diamondbacks actually excelled at getting ahead. Their 64.1 percent first-pitch strike rate was tied for the sixth-highest mark in the majors.

Several of the club’s top inning-eaters, including Brandon Pfaadt, Ryne Nelson and Slade Cecconi, were elite in this regard. Of the 15 D-backs pitchers who threw 30 or more innings in 2024, only two had below-average first-pitch strike rates: Bryce Jarvis (59.3 percent) and Zac Gallen (58.7 percent).

Of course, getting ahead in the count only gets you so far. Once D-backs pitchers got to two strikes, they often stumbled. Only 18.5 percent of their two-strike pitches resulted in a strikeout, the seventh-lowest mark in the league. (This metric is known as putaway percentage.)

Cecconi and Montgomery struggled mightily in this regard, with putaway rates of just 15.4 percent and 15.1 percent, respectively. For Montgomery, that figure is alarming. His putaway rate last year was 19.6 percent, and it had never been lower than 18.9 percent in any previous season. That explains why Montgomery’s strikeout rate plummeted to a career-low 15.6 percent this year.

Bizarrely, Montgomery actually generated swinging strikes at a higher rate in 2024 than he did last year. Search up a leaderboard for whiff rate in 0-0, 0-1 and 1-0 counts, and you’ll find Montgomery’s name up there alongside some of the best pitchers in the game — and ahead of Pittsburgh Pirates star rookie Paul Skenes. For whatever reason, that swing-and-miss ability cratered as at-bats wore on.

Now, back to the big picture. We have established that D-backs pitchers struggled to put hitters away, but why was that? Pitch location does not seem to be the primary issue.

In two-strike counts, Diamondbacks pitchers evacuated the zone at an above-average clip, and a healthy portion of those pitches landed in the chase region, which is a few inches away from the outer edges of the strike zone and generally excellent for inducing whiffs.

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Even when spotting two-strike pitches in ideal locations, D-backs pitchers struggled to generate whiffs. In 2024, their whiff rate on two-strike pitches in the chase region was tied for the seventh-lowest mark in the league. More broadly, they had the third-lowest whiff rate in the league on two-strike pitches that were outside the zone.

Granted, there is more to pitching than strikeouts; generating soft contact is also a viable way to get outs. But the Diamondbacks struggled in that regard, too. Based on both actual and underlying expected stats on balls in play, the Diamondbacks were the second-worst team in baseball at limiting hard contact, ahead of only the Colorado Rockies.

Poor location would be an easy explanation, but, once again, the numbers tell a different story. In 2024, D-backs pitchers threw fewer pitches in the heart of the strike zone than all but four major-league teams. Meanwhile, they led the league in rate of pitches in the shadow zone, which covers the area on and around the edges of the strike zone.

By all indications, the Diamondbacks were one of the better teams in the league at locating pitches this year. Nonetheless, not only did they fail to miss bats, but they failed to miss barrels. While there is no singular explanation for the Diamondbacks’ pitching woes in 2024, it seems reasonable to question whether the club is lacking in raw stuff.

Pitchers with great stuff — which includes factors such as velocity, spin and movement — generally excel at missing bats and getting away with mistakes. The Diamondbacks struggled on both fronts. On pitches in the heart of the zone, they got hit harder than any team in baseball.

To be clear, this does not mean that the Diamondbacks need to go out and sign a bunch of guys who throw 100 mph. That might be great, but it probably isn’t realistic. Pitchers who miss a ton of bats are expensive, and the Diamondbacks do not have much room on their roster for external pitching additions this offseason anyway.

For the moment, the more reasonable goal might be trying to help their pitchers maximize the stuff they already have. Better injury luck would help, too. All of the Diamondbacks depth starters who filled in due to injury this year had below-average strikeout rates. Relying on them less — or helping them find ways to miss more bats — could go a long way in improving some of these underlying stats.

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Setting the numbers aside for a moment, there is one other Diamondbacks pitching narrative that warrants mentioning: the fact that former pitching coach Brent Strom seemingly was not on the same page with his pitchers — at least not all of them. Strom alluded to this last month, although he did not offer specifics.

“I had a feeling that regression might take place with some people, although it’s just normal,” Strom said. “There’s some major issues that need to be addressed. I’m not going to go into it now. It’s an in-house type thing. I think there are things that we can do to improve.”

Whatever was going on behind the scenes, the Diamondbacks reportedly fired Strom as pitching coach last week. The club also moved on from pitching coordinator Dan Carlson and bullpen coach Mike Fetters.

With a fresh slate of pitching coaches in 2025, the Diamondbacks will look to bounce back from one of the most disappointing pitching performances in franchise history.

The results were dire this year, but there is hope. On paper, there is still plenty of talent on this roster. With a few tweaks and better injury luck, it’s not all that hard to imagine a Diamondbacks pitching staff that is vastly improved next year.

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Top photo: Ron Chenoy/Imagn Images