The MLB trade deadline deals that'll make the biggest immediate impact, according to the data

“Your goal shouldn’t be to buy players, your goal should be to buy wins.” -Jonah Hill, as Peter Brand, as Paul DePodesta in "Moneyball"

The MLB trade deadline is often seen as the movement of players and money, and it is indeed that. But behind all these moves is a sea of numbers, numbers that are not more important than the players themselves but do help illustrate the thought process behind these often extraordinarily complex trades. What do these numbers tell us about who really won and lost deadline season? Let's dive in and find out.

Projection models are an important tool during the trade deadline

For the below exercise, I’m relying on ZiPS (aka “Zymborski Projection System”, developed by Dan Szymborski) to see how much fWAR each major addition is bringing to their new team. It’s an interesting way to look at these acquisitions relative to each other, as while there are also some projected wins going out the door, generally we have a fairly lopsided equation for the rest of this season. The Boston Red Sox, for example, gave up several valuable Minor League prospects to land catcher Adley Rutschman, but none pf those prospects will provide the Baltimore Orioles with any MLB value in 2026.

Disclaimer: Because of an annoying thing called time constraints, this is a slightly inexact science. ZiPS updates quite regularly, but these are ROS calculations which will change once all the dust settles from the deadline. They will not change that much, though, and the below takeaways will be broadly true either way. 

1. LHP Tarik Skubal, Los Angeles Dodgers

• ZiPS fWAR (ROS): +1.8
• Immediate impact: seismic

Skubal is a perfect example of the kind of value a single trade can provide. A total of 1.8 fWAR, for most guys, is a solid Major League season — you can make a living with that. Skubal, meanwhile, can manage that in less than a third of a season. It’s hard (for me at least) to exactly quantify how many wins were lost by Skubal swallowing up a spot in the rotation, since Dave Roberts could play that a number of different ways. In any case, he is worth quite a bit.

But if you or someone you love was freaking out about the Dodgers getting Skubal, this is a good number to point to. He’s just a destiny-tilting force who provides instantaneous value for an L.A. rotation that does not even remotely need the help. It feels downright unfair, honestly. The first shall be first. 

2. C Adley Rutschman, Boston Red Sox

• ZiPS fWAR (ROS): +1.2
• Immediate impact: league-tilting

Rutschman is another example of the type of player that fits so well in a lineup that their impact can be even larger than the WAR suggests.

Rutschman fills a cavernous hole in the Red Sox lineup. Catcher has been a black hole for years in Boston with Carlos Narvaez and Connor Wong patching together a passable approximation. Season over season, Rutschman could be worth as much as +4.0-5.0 WAR to Boston, which is why they gave up such value in the deal. That stuff doesn’t grow on trees.

3. 2B Luis Arraez, Philadelphia Phillies

• ZiPS fWAR (ROS): +1.0
• Immediate impact: major but disruptive

Arraez is a player I’ve covered in detail this season given his very-hard-to-explain surge as an elite defensive second baseman. But he’s keeping it up and projects as one of the most impactful additions of the deadline to a team that desperately needs hitting. Bryce Harper and Kyle Schwarber are the only thing the Phillies have going offensively, and Arraez will slot right into the order in a spot of serious need. 

But it does come with a highly disruptive, if not literally reductive, cost. Putting Arraez at second means moving Bryson Stott to third which means moving Alec Bohm to first which means moving Bryce Harper to right field … apparently. That may have some unintended consequences when your entire infield moves around and none of it involves improving Trea Turner’s spot, where he's been one of the worst defensive shortstops in baseball. Arraez definitely adds value, but there could be unintended consequences.

4. RHP Kevin Gausman, Chicago Cubs

• ZiPS fWAR (ROS): +1.0
• Immediate impact: huge but temporary

To say the Cubs needed to improve their starting rotation is to say a teacher needs students or that a bird needs the sky. Chicago understood the assignment and added Gausman, still an above-average arm with ace capabilities even if he is a pure rental, along with Clay Holmes and Braxton Garrett to bolster their staff.

Gausman projects to add an entire win for the Cubs in 2026 but projects to add exactly zero in 2027 (if such a season exist; lockout feels likely idk if you heard), which is an important element of the trade deadline to consider. Other than Rutschmann, our entire list is playing on rental contracts, given that most teams are not inclined to trade valuable players with years of team control remaining. Rutschman had one additional year and cost an arm and a leg compared to Skubal costing a single finger. 

5. RHP Casey Mize, San Diego Padres

• ZiPS fWAR (ROS): +0.8
• Immediate impact: large … at a cost

For teams stuck in the middle, there's an important question to answer: Do you want to add wins right now, or do priorities need to shift to the farm system? The Padres, who are four games above .500 but sitting third in the brutal NL West, have relentlessly pursued a win-now approach under AJ Preller, and now it feels like the only ending to this story is a World Series or Preller’s firing. Already the least valuable farm system in the sport, San Diego quadrupled and quintupled down at the deadline with moves for rental pitchers Robbie Ray and Casey Mize to make a last-ditch run at the postseason. 

WAR was added, rotations were improved, but is any of it the right move? The Padres are talented, sure, but they simply do not have the requisite playoff odds to be going all-in on rentals like that. If it works, it works. If it doesn’t … well, you know how that usually ends for front offices. 

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