Mason Miller trade grades: Padres get credit for huge swing, A’s nail deal with ‘A’ return of top prospect

The San Diego Padres and Athletics agreed to a blockbuster deal on Thursday, hours before Major League Baseball’s July 31 trade deadline passed (6 p.m. ET). The Padres will add All-Star right-hander Mason Miller and veteran lefty JP Sears to their pitching staff in exchange for a package fronted by shortstop prospect Leo De Vries. The Athletics will also receive three righties: Braden Nett, Henry Baez, and Eduarniel Núñez.

As is tradition around these parts, CBS Sports provides instant analysis whenever a notable trade goes down. That includes, among other aspects, handing out a letter grade to both sides. You’ll find that exercise below. First, though, here’s a breakdown of the trade in whole:

• Padres receive: RHP Mason Miller and LHP JP Sears
• Athletics receive: SS Leo De Vries, RHP Braden Nett, RHP Henry Baez, and RHP Eduarniel Núñez

Onward.

Padres grade: C

A lot of baseball management concerns risk. How you evaluate it, how you work with or around it. Certain front offices get the reputation for being risk averse, which isn’t necessarily an insult. On the other end of the spectrum is Padres general manager AJ Preller. There might not be a single executive in the game with a higher risk tolerance. You get the sense he’s fond of it.

Put another way, Preller might be the only contemporary executive with the stomach to make this particular trade, shipping off one of baseball’s top prospects (plus a few others who should develop into contributors in some form or another) for what amounts to an injury-prone reliever and a back-end starter. Love it, hate it, but you have to admire it on some level, for it makes an at-times overly staid industry a heck of a lot more entertaining.

Miller, 27 come late August, is one of the best relievers in baseball. He’s notched a 3.16 ERA (129 ERA+) and a 3.65 strikeout-to-walk ratio in 136 innings since debuting in 2023. It would be reasonable to describe him as a baseball pyromaniac: his fastball clocks in at 101.1 mph and, when he wants to take a little off, he turns to an upper-80s slider that has generated more than 50% whiffs this season. To restate that a little: batters have missed on more than half their hacks taken against Miller’s slider. That’s how one ends up averaging 14 strikeouts per nine innings.

Miller is under team control through the 2029 season, but other front offices have speculated about his availability since the minute he established himself at the big-league level. That’s because he appears to be a highly unreliable quantity; even now, in his age-26 season, he’s yet to throw as many as 100 innings in a year. It’s not from a lack of trying: he was a starter until 2024, at which point the Athletics conceded that some arms just can’t withstand the starting rigors.

All of which makes Miller’s long-term value more of a mystery box than this trade indicates. To add to the intrigue: the Padres reportedly view Miller as a potential candidate to start again. They’ve had success turning relievers into starters before, including Michael King and Stephen Kolek, but this is an interesting equation to compute. Is the risk of injury greater than the potential reward? What about when all indications suggest that the probable success likelihood is … well, improbable? Stay tuned on this one. There’s a lot of fog to be cleared.

Sears, 29, is under team control through the 2028 season, making him a potential long-term fit at the back of San Diego’s rotation. Across four seasons with the A’s, he compiled a 4.59 ERA (88 ERA+) and a 2.89 strikeout-to-walk ratio. Sears relies heavily on a three-pitch mix: a low-90s four-seamer, a sweeper he could probably stand to throw more often, and a changeup. He’s an extreme fly-ball pitcher, generating just 28.2% grounders to date, and he ought to benefit from fleeing the Sacramento launching pad. That doesn’t mean Sears is going to magically morph into a frontline starter; it does, however, suggest the best part of his season awaits. 

So, is this a good trade? Based on probabilistic analysis … eh, probably not. It is worth viewing and consuming this move for what it is: part of a sequence rather than a standalone. That’s why the Padres earn the “C” grade here: it’s a hedge that things will look better by nightfall. (Hey, executives aren’t the only ones who deal in risk on deadline day.) Now, Preller can trade some of his other pitchers, like starter Dylan Cease and closer Robert Suarez, in his pursuit of shedding money and adding offense. We’ll see what shape, exactly, the Padres roster is in come August. But, if there’s one thing you can bank on in these volatile hours of this unpredictable sport, it’s that Preller is going to swing for the fences.

Athletics grade: A

On the subject of risk, how about this side of things? The A’s successfully turned a volatile reliever (in health if not performance) and someone who might’ve been a non-tender candidate for them sooner than later into one of baseball’s top prospects — plus a few other arms. We’ll find out over the coming years if De Vries can deliver on his promise, but it’s a nice-looking piece of business.

De Vries, 18, is the crown jewel here. He’s a switch-hitting shortstop who, despite being four years the junior of his average competition, has hit .245/.357/.410 with reasonable strikeout (19.6%) and walk (14.1%) rates. Demonstrated competency as such a young age tends to be a great predictor of future success. That, plus De Vries’ obvious physical tools, make it easier to overlook or wave off some of his blemishes. (For instance, he’ll need more of his power potential to manifest in games.) Even if he falls short of expectations, there’s a chance he reaches maturation with five average or better tools. That makes him an awfully enticing addition.

Nett, 23, is a former undrafted free agent the Padres unearthed at St. Charles Community College. (That’s in Missouri, for those curious.) He’s penning one heck of a story, having spent this season in Double-A, accumulating a 3.39 ERA and a 2.53 strikeout-to-walk ratio in 74 innings. Nett’s mid-90s fastball is his best offering, but he has a full arsenal with a few other average or better pitches at his disposal. He’s been prone to walking enough hitters (nearly six per nine innings to date in his professional career) that it’s possible he ends up in the bullpen because of it.

Baez, 22, is a big righty who has compiled a 1.96 ERA and a 2.87 strikeout-to-walk ratio across 20 starts in Double-A. Those numbers are more impressive than the actual package is, though it’s fair to give him extra credit for the deception he generates with an extreme crossfire delivery. There’s a big-league contributor here, and there’s no reason for the A’s to move him to the bullpen until they have to, should that moment ever actually arise. (Do note that, as with Núñez below, Baez is already part of the 40-man roster.)

Núñez, 26, has appeared in four games this season at the big-league level. He’s a tall and lean right-hander with a short arm stroke who pumps upper-90s fastballs and sliders — the latter of which has generated a 50% whiff rate between Triple-A and the majors. Núñez does have a wretched history of throwing strikes, with this season on pace to represent the first time in his professional career he’s cleared the 20-inning threshold and averaged fewer than five walks per nine. If the A’s can keep him on the straight and narrow path to the strike zone, he just might end up taking some of those high-leverage opportunities that would’ve previously been Miller’s.