After a busy offseason that already drew widespread praise, the Diamondbacks made arguably their most impactful move of the winter on Tuesday by reportedly agreeing to terms with left-handed starter Jordan Montgomery on a one-year, $25 million deal.

According to multiple sources, Montgomery can also trigger a $20 million player option for 2025 by making at least 10 starts this season. That figure balloons to $22.5 million if he makes 18 starts and $25 million if he makes 23 starts or more.

Montgomery, 31, is coming off the best year of his career. In 2023, he had a 3.20 ERA, 1.19 WHIP and 166 strikeouts compared to 48 walks in 188.2 innings. He spent the first half of the season with the St. Louis Cardinals before being traded to the Texas Rangers at the deadline.

After a stellar finish to the regular season with his new team, Montgomery played a significant role in the Rangers’ run to a World Series championship, posting a 2.90 ERA in 31 innings across six postseason appearances. Ironically, his only loss in the playoffs last year came against the Diamondbacks in Game 2 of the World Series.

The notion of Montgomery signing a short-term contract might have seemed impossible several months ago. Entering the offseason, he was widely expected to command a nine-figure deal spanning upward of four or five years.

Clearly, Montgomery’s market was not as robust as agent Scott Boras hoped. In that regard, Montgomery is not alone. Several Boras clients have signed for below industry expectations in recent days, including outfielder Cody Bellinger, third baseman Matt Chapman and starting pitcher Blake Snell.

Last week, Snell signed a two-year, $62 million contract with the San Francisco Giants that included an opt-out after the first year. The Diamondbacks’ deal with Montgomery closely mirrors that one.

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How Montgomery fits with Diamondbacks

Since Montgomery missed out on spring training, he is expected to open the year in the minors before joining the Diamondbacks, according to multiple reports. That means that the starting rotation manager Torey Lovullo announced on Tuesday — Zac Gallen, Merrill Kelly, Tommy Henry, Brandon Pfaadt, Ryne Nelson — should hold for the time being.

However, once Montgomery’s ramp-up is complete and fellow offseason signee Eduardo Rodriguez has returned from a lat strain, the Diamondbacks could have one of the better starting rotations in baseball.

Last year, there were 15 pitchers in all of MLB with 150 or more innings pitched and an ERA+ of 125 or higher. The Diamondbacks now have four of them with Gallen, Kelly, Rodriguez and Montgomery. No other team has more than two.

Granted, underlying metrics suggest that the aforementioned Diamondbacks quartet could regress in 2024. Montgomery is no exception.

In 2023, his 3.20 ERA outpaced his FIP (3.56), xFIP (4.01), xERA (3.98) and SIERA (4.23). That is statistics’ way of saying, “This might have been unsustainable.”

Still, Montgomery’s success in 2023 was far from a blip in the radar. In 2022, he posted a 3.48 ERA and 1.09 WHIP in 178.2 innings with the New York Yankees and Cardinals. He spent the entirety of the 2021 season with the Yankees, notching a 3.83 ERA in 30 starts.

Over the past three seasons, Montgomery is one of 20 major-league pitchers who has amassed 500 regular season innings. His 3.48 ERA in that span ranks 11th in the group, just behind Seattle Mariners ace Luis Castillo and just ahead of newly acquired San Diego Padres starter, Dylan Cease.

As for whether Montgomery will be worth the $25 million he is reportedly owed this year, that, of course, remains to be seen. Fangraphs’ ZiPS projections system has Montgomery pegged for 3 WAR in 2024, which translates to around $27 million of value in free agency. On paper, the price tag checks out.

Montgomery’s 2024 salary is the highest of any player in D-backs history not named Zack Greinke. It also pushes the Diamondbacks’ payroll farther into record-breaking territory, now around $170 million.

The move brings to mind general manager Mike Hazen’s comments from Day 1 at the winter meetings in early December, when he said that adding multiple starters this offseason “would be the ideal outcome.”

What makes Montgomery effective

Much like the rest of the Diamondbacks’ rotation, Montgomery is not overpowering, but he has a wide array of weapons and he knows how to use them. His 21.4 percent strikeout rate in 2023 was around league average, but his 6.2 percent walk rate ranked in the 82nd percentile.

Montgomery throws five pitches: a sinker, changeup, curveball, four-seam fastball and cutter.

Last year, he relied on his sinker more than ever, throwing it a career-high 42.6 percent of the time. The results were promising. Based on Statcast’s run value metric, Montgomery’s sinker was the fifth-most valuable sinker in all of baseball.

In addition to throwing his sinker more than ever in 2023, Montgomery also threw it harder than ever. His 93.3 mph average sinker velocity last year was a career high. The pitch has above-average arm-side run, meaning it tails away from righties and in toward lefties more than a typical sinker.

Here is a look at a particularly good one to D-backs outfielder Alek Thomas in April of last year:

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By run value, Montgomery’s next best pitch in each of the past three seasons has been his curveball — or his “Death Ball,” as his coaches at Tread Athletics called it last offseason.

On paper, the pitch’s spin and movement are quite ordinary, but Montgomery tunnels it masterfully with his sinker, and his high release point is perfect for throwing a pitch like this one, as detailed in this helpful Death Ball tutorial from Lance Brozdowski.

In 2023, opposing batters hit just .191 against Montgomery’s curveball and came up empty on 37.1 percent of swings against it. For reference, the league average whiff rate on curveballs last year was 31.2 percent.

Unlike his changeup, Montgomery uses his curveball frequently to both lefties and righties.

Here is an example of a nasty one to a familiar left-handed hitter, former D-backs outfielder Daulton Varsho:

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And here is one to a right-handed hitter, current D-backs first baseman Christian Walker:

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Montgomery upped his curveball usage last September and did so even more dramatically in the playoffs, throwing it 31.5 percent of the time. It will be interesting to see if those changes carry over to the 2024 season.

Whether they do or not, Montgomery’s changeup still figures to be a key weapon against right-handed hitters moving forward. He held righties to a .696 OPS last year, in large part because of that pitch.

In similar fashion to the curveball, Montgomery’s changeup had a 39.2 percent whiff rate last year, well above the league average of 31.1 percent on that pitch type. Opposing batters hit .239 against it in 2023.

Montgomery’s changeup is unique in that it is remarkably effective when in the strike zone. Last year, Montgomery had the second-best whiff rate in all of baseball on changeups in the strike zone (minimum 150 pitches), trailing only the aforementioned NL Cy Young winner, Blake Snell.

Here is Montgomery striking out former Diamondbacks outfielder Tommy Pham on a changeup that caught the lower outside corner:

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As far as his four-seam fastball is concerned, Montgomery backed off the pitch considerably in 2023 — the numbers leave little doubt that his sinker is the more effective weapon overall — but he kept it around as a distant fourth offering.

In two-strike counts, Montgomery would use it on occasion to change eye levels.

Here, he did exactly that to Eugenio Suárez:

In many ways, watching Montgomery is similar to watching Gallen or Kelly.

He does not throw 98, nor does he possess a Spencer-Strider-esque breaking ball. But he does a good job getting the most out of what he has. And that’s been enough to make him one of the most effective starters in the league for several years straight.

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Top photo: Kim Klement Neitzel/USA TODAY Sports