Wait. Stop. Take a second and look at the St. Louis roster today. It looks weird, doesn't it? The biggest shocker of the 2026 offseason just landed like a lead weight in the desert. We’re talking about the Arizona Diamondbacks vs St. Louis Cardinals deal that finally sent Nolan Arenado back to the NL West.
Honestly, it feels like the end of an era. Or maybe the start of a very strange one.
For years, the Cardinals were the "gold standard" of the National League. You knew what you were getting: stability, veterans, and October baseball. But the 2025 season changed the math. St. Louis finished 78-84, a middling record that signaled a desperate need for a rebuild. Meanwhile, the Diamondbacks—stuck in that awkward "good but not great" 80-win limbo—needed a spark. They needed a third baseman who didn't feel like a revolving door.
So they did it. They traded for a 10-time Gold Glover who, quite frankly, looked a bit washed last year.
The Blockbuster Trade That Shook Both Fanbases
Let's get into the weeds of this Arizona Diamondbacks vs St. Louis Cardinals trade. It’s not your typical superstar swap. Usually, when a guy like Arenado moves, you expect a haul of top-100 prospects. Not this time.
St. Louis sent Nolan Arenado and a mountain of cash—$31 million of his remaining $42 million—to Phoenix. In return? They got Jack Martinez.
Who?
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Exactly. Martinez was Arizona’s eighth-round pick in 2025 out of Arizona State. He hasn't even thrown a pitch in professional ball yet. It sounds like a fleecing on paper, but it’s more complicated. Chaim Bloom, now running the show in St. Louis, basically paid $31 million just to make the Arenado era go away. It’s a "reset" move. The Cardinals are officially handing the keys to the kids like Masyn Winn and Jordan Walker.
Arenado himself admitted he felt like an "obstacle" to the Cardinals' growth. That’s a heavy word for a future Hall of Famer to use. He’s 34 now. Last year, he hit .237 with only 12 home runs. Those aren't Arenado numbers. Those are "my back and wrist hurt" numbers.
But for the Diamondbacks? It’s a gamble worth taking. They’re only paying $11 million over two years for a guy who might just need a change of scenery to find his power again. If he hits 20 homers and plays elite defense, Arizona wins this trade by a landslide.
Why the 2025 Season Series Flipped the Script
If you want to know why this trade happened, you have to look at how these two teams played each other last summer. The 2025 head-to-head matchups were a disaster for St. Louis.
Remember the July series at Chase Field?
The Diamondbacks absolutely dismantled them. In one specific game on July 19, 2025, Eugenio Suárez went off for two home runs while Corbin Carroll slapped two triples. The D-backs won 10-1. They followed that up the next day with a 5-2 win to complete a three-game sweep.
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- Arizona's Dominance: They outscored the Cardinals 22-6 over that three-game stretch.
- Pitching Woes: Sonny Gray—who has since been traded to the Red Sox—got tagged for eight earned runs in just 3.3 innings during that series.
- The Turning Point: That weekend in Phoenix was arguably the moment the Cardinals' front office realized the "win-now" window had slammed shut.
Arizona finished the 2025 season series with a clear upper hand, especially at home. They looked younger, faster, and much more athletic than the aging Redbirds. It’s no wonder Torey Lovullo wanted to add a veteran presence like Arenado to stabilize a clubhouse that has plenty of talent but occasionally lacks that "been-there-done-that" grit.
Breaking Down the Matchup: By the Numbers
When you look at the Arizona Diamondbacks vs St. Louis Cardinals historical rivalry, it’s historically lopsided. The Cardinals have dominated the all-time series 112-72. But history doesn't hit a curveball.
Current trends show a massive shift. The Cardinals are officially in a "reconstruction phase." They’ve offloaded Sonny Gray, Willson Contreras, and now Arenado. They are lean, cheap, and very unproven.
Arizona is the opposite. They are leaning into their window. With Zac Gallen and Merrill Kelly (who went 9-5 with a 3.34 ERA in 2025) leading the rotation, they have the pitching to compete. The big question is whether their offense can stay consistent. Corbin Carroll had a "down" year by his standards in 2025, despite leading the league in triples. If he bounces back and Arenado finds even 70% of his old self, the NL West needs to watch out.
The Personnel Pivot
- St. Louis focus: High-upside arms like Jack Martinez and letting Masyn Winn (who hit 6 homers in early 2025) take over as the face of the franchise.
- Arizona focus: Maximizing the remaining years of the Gallen/Kelly duo by plugging the hole at third base with a legendary defender.
- The X-Factor: Eugenio Suárez. He was the hero of the 2025 matchups against St. Louis, but with Arenado coming in, his role is suddenly in question. Does he move to DH? Is he trade bait?
What to Expect Moving Forward
Going into the 2026 season, every Arizona Diamondbacks vs St. Louis Cardinals game is going to have a weird vibe. You’ll see Arenado in a Sedona Red jersey facing off against a Cardinals lineup that might feature three or four rookies.
It’s sorta bittersweet.
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If you’re a Cardinals fan, you’re looking for glimpses of the future. You want to see if Jordan Walker can finally become the monster everyone predicted. You’re watching the box scores for Jack Martinez in the minors to see if the Arenado "salary dump" was worth it.
If you’re a Diamondbacks fan, you’re holding your breath. You’ve seen this movie before—trading for a veteran past his prime—and it doesn't always end well. But the defense? The defense will be incredible. An infield with Arenado at third and Ketel Marte (who put up a massive 6.8 WAR in 2024) at second is a pitcher's dream.
Basically, the power dynamic has shifted. The Cardinals are no longer the big brother in this matchup. Arizona is the aggressor now.
To get the most out of this new rivalry dynamic, keep an eye on the early April series. Watch how the St. Louis crowd reacts to Arenado’s return. More importantly, watch how the Diamondbacks' young pitchers like Ryne Nelson—who dominated the Cards in July 2025—handle a revamped, younger St. Louis lineup. The "safe" bet of the Cardinals winning the season series is officially a thing of the past.
Check the updated 2026 schedule for the first meeting at Busch Stadium; that homecoming will tell us everything we need to know about who actually won this trade.