Padres Swing Big in Deal for Mason Miller

It was shaping up to be a boring trade deadline day, with the most interesting rental, Eugenio Suárez, already off the board and no huge prospects or stars in play. But the San Diego Padres don’t limit themselves to the guys that everyone knows are on the block. They swung a massive, unexpected deal earlier today, getting Mason Miller and JP Sears from the Athletics in exchange for Leo De Vries, Braden Nett, Henry Baez, and Eduarniel Núñez, as ESPN’s Jeff Passan first reported.

Miller burst onto the scene last year with one of the great relief seasons of the decade. He ramped up his fastball to nuclear velocities, sitting 100-101 mph and topping out above 103 en route to a 41.8% strikeout rate and a 2.49 ERA with peripherals that were even better. He did all that over 65 innings, a career-high workload for the 2021 draft pick. His fastball is a pitch modeler’s dream, all backspin and flat approach angle, and his slider is nearly unhittable for batters thinking “don’t get put on a poster by this fastball” from the minute they step into the box.

Miller’s 2025 encore hasn’t gone quite as well. For relievers not named Mariano Rivera, that tends to be the case. He’s still breathing as much fire as ever, but he’s aiming it a bit less effectively, and his walk rate has ballooned from 8.4% to 11.9%. Oh, don’t get me wrong, he’s still been very effective. Did you miss the part where I said he throws 103 with great shape and mixes in a nasty slider? Of course he’s still been effective. The decline has only been on the margins — ERA estimators in the high 2.00s instead of the low 2.00s, a low strand rate, and bam, suddenly he has a 3.76 ERA instead of a 2.49 mark. His stuff still looks really good, it’s just hard to maintain a two-handle ERA. Those are the numbers you put up when things go right, and 2025 seems more like an average year for Miller.

Do the Padres need that skill set right now? I don’t think so, which is making me go full A Beautiful Mind while I think about the implications of this trade. San Diego’s bullpen is the best in baseball. Closer Robert Suarez and setup man Adrian Morejon have both outperformed Miller in pretty much every metric this year. So has Jeremiah Estrada, whom I had pegged as the team’s closer-in-waiting before this trade. I haven’t even mentioned Jason Adam, who’s on his second straight year of a sub-2.00 ERA. Yes, it’s fun to build the whole bullpen out of closers, but there are diminishing marginal returns at some point. The four guys I’ve already mentioned are the only Padres relievers who have come into the game in spots with a higher-than-average leverage index this year. In other words, they’re already soaking up all the most important times to use good relievers. Miller will probably get the highest-leverage spots now, but that means less tight games for Estrada, Morejon, and Adam.

One possibility that could clear things up a little: The Padres could trade Suarez. Preller is no stranger to buying and selling at the same time, and Suarez can opt out of his deal after this year. Given the prices flying around for relievers at the moment, and particularly given that Preller himself has raised the ante with this trade, Suarez could fetch an attractive prospect return later today. Heck, so could Morejon or Adam if the Padres want to retain Suarez and trade a lower-leverage guy with an extra year of team control.

This is speculative, of course. I’m just trying to figure out why the team that perhaps least needed a great closer went out and got a guy so good that it wasn’t even clear he was on the market. That’s the most likely reason for me, but let’s try a few others on for size before getting to the return. Heck, we haven’t even talked about the other player San Diego got yet. That would be Sears, and that brings me to my next theory: The Padres really just need starters.

The left-handed Sears went from the Yankees to the A’s as one of the key parts of the Frankie Montas trade in 2022. He’s been a fifth-starter type ever since, with ERAs in the mid-4.00s in the Oakland Coliseum before this season and the high 4.00s in launching-pad Sacramento. He’s a fly ball pitcher with plus command and fringy stuff, an absolute nightmare in a hitter’s ballpark. He’s sneaky old for a guy who didn’t graduate from prospect status all that long ago – he’ll turn 30 this winter – but won’t hit free agency until after the 2028 season. Even if you don’t know Sears specifically, you can probably picture a guy like him on your favorite team. He absolutely deserves a major league roster spot, and you’d much rather see him take the mound than some of the other options your team has thrown out there this year, but you probably wouldn’t want him starting a playoff game.

The Padres also definitely don’t want Sears to start a playoff game. They have Nick Pivetta, Dylan Cease, Yu Darvish, and Michael King (slated for a rehab start this weekend) for that. But right now, Sears is their fifth starter, and adding him enabled them to trade two other starting pitchers, Stephen Kolek and Ryan Bergert, in a separate trade.

There’s even a chance they could use Miller as a starter, as Dennis Lin and Ken Rosenthal of The Athletic reported last night. If you’re into chess notation, I give that option a “?!”. Maybe it’s a good move. Maybe it’s an awful one. It’s certainly an unexpected option. We’re talking about a guy who lives off of his explosive, triple-digit fastball and throws only two pitches. Miller was developed as a starter, but only kind of; his largest workload before converting to relieving was 52 2/3 innings across four levels in 2023. His delivery is so sudden and violent that he dealt with injuries throughout his tenure as a starter: a scapula strain in 2022 and a UCL strain in 2023.

The unknowns don’t stop there. He’s great with two pitches. His third and fourth offerings are less polished. He’s running a 12% walk rate in short stints. This isn’t your usual starter conversion package. But after Garrett Crochet’s successful transition from lights-out reliever with injury issues to one of the best starters in baseball, and given Miller’s hulking build, I can see why the Padres might at least be willing to consider him for a starter’s role. I don’t think it’s very likely to stick. I certainly don’t think it’s going to happen this year. But given how valuable starters are and how impermanent reliever performance seems to be, I don’t hate that they’re going to take a look.

That’s the San Diego side of the trade. The Athletics’ return for Miller and Sears contains both quality and quantity. The headliner is Leo De Vries, either San Diego’s best or second-best prospect depending on how you feel about the injured Ethan Salas. De Vries is an 18-year-old switch-hitting shortstop who was the top signing of the 2024 international class. As is customary for San Diego’s top minor leaguers, he was dealing with a tremendously aggressive assignment: High-A Fort Wayne, where he was 4 1/2 years younger than the average player. He more than held his own there, walking almost as often as he struck out and displaying gap-to-gap power.

We have him graded as a 50 FV, right on the borderline of 55 FV, but other outlets have him squarely in that higher tier. Our prospect team sees him as more polished than toolsy, with already-mature skills and a precocious feel to hit. He’s more comfortable batting lefty than righty at the moment, to the point that he briefly stopped switch-hitting in 2024, but he’s back to doing both again and looks good from each side.

There’s a ton of projection here, of course. We’re talking about an 18-year-old who only started playing professional baseball in 2024. I’m excited about De Vries not for his raw performance but for the fact that he’s doing it in full-season A-ball despite his age. That means the next few years are key; the range of outcomes is massive and the trajectory is both uncertain and important. In two years, we’ll probably feel very differently about De Vries than we do now. His ceiling is certainly high, though, as it would be for any 18-year-old hitting better than league average at such an advanced level. He even plays shortstop, though whether he’ll stick there as he gains strength is an open question.

De Vries is the unquestioned headliner, but the A’s got three other minor leaguers in the deal, and all of them are intriguing. Nett is the best of the trio, a 40+ FV starter working in Double-A at age 23. He throws hard and has continually improved his command since signing with the Padres as an undrafted free agent in 2022. His 10.4% walk rate is easily the best of his career, and he’s missing a ton of bats with an upper-90s fastball plus an array of solid secondaries. With strike throwing the prime directive at the moment, Nett has shelved his slider in recent months, instead mixing in a cutter, curveball, and changeup. I’m not sure whether he’ll be a starter or a reliever once he’s a finished product, but I think he could be pretty good in either role; he has the raw stuff to excel as a short-stint reliever, but his development arc thus far gives me hope that he’ll keep refining his pitchability and secondary stuff over time, enough to remain in the rotation. We have him graded as a multi-inning reliever at the moment, but with considerable volatility around that.

Baez projects as a fifth starter, and I actually think he’ll debut soon; he’s already on a 40-man roster and the A’s could use some pitching. He looks like a depth piece both to me and the prospect team, with a bunch of average pitches and decent but unspectacular command. He doesn’t miss many bats, but he doesn’t walk many batters either, and he gets a ton of grounders. For now, he’s probably no more than an up-and-down pitching option, but he has so many peripheral skills that he could raise his ceiling a bit if his stuff takes a step forward. I’d be interested in seeing him in the majors this year, even if he’s probably not quite ready. Depending on how the rest of the roster shakes out, Baez could be at risk of getting outrighted off the 40-man this winter, but that’s why the A’s should give him a look before they have to make that decision.

The last player in the deal, Núñez, had a cup of coffee in San Diego at the start of the month and is back in Triple-A. He has ludicrous stuff and subpar command of it. His minor league swinging strike rates jump off the page, but unfortunately so do his walks. If he could repeat his delivery more consistently, he’d be wild but unhittable in the big leagues. During his brief time in the majors, our pitching models said exactly the same thing: elite stuff, some of the worst command in the sport. He sits 97-98 with his fastball and drops in two different hard breaking balls. His curveball is mid-80s with big two-plane movement. Eric Longenhagen noted that the A’s have done a better job with pitching development of late and that a change of scenery can sometimes unlock consistency gains, but Núñez seems to be the least consequential of the five players involved.

The easier side of this trade to grade, at least to me, is the nomadic Athletics one. They’re going nowhere this year, but they have a fun young core to build around. They turned an exciting reliever from their current squad into a haul of prospects that features a potential future star. If I were running a major league team and not currently in playoff contention, I’d be looking to trade as many of my good relievers as possible. You need a good bullpen to succeed in the majors, but it’s extremely difficult to know which relievers will be good in two years. I’d prefer to figure that out as I go by building a deep farm system, signing free agents, and making trades as necessary rather than relying on a singular ace closer. In other words, I’d be looking to trade Mason Miller for Leo De Vries.

Yes, Miller is currently great, but as my colleague Michael Baumann is always pointing out, team control of relievers is often fool’s gold. The half life of an effective reliever is short. The top five relievers of 2023 were Tanner Scott, Félix Bautista, David Bednar, Matt Brash, and Camilo Doval. Bednar is the only member of that group who has been both healthy and effective this year – and he was below replacement level in 2024! That’s a particularly unsuccessful comparison group, but “don’t bet on relievers staying good for multiple seasons” is just smart business. Don’t do it! It won’t pay off!

The Padres might not care about that much, though. For one thing, they value the present a ton more than the A’s do. They’re in a playoff race right this instant and are looking to make a deep postseason run, and while Miller’s value in 2027 and beyond is hard to pin down, he is incredibly valuable this year. He’s one of the best relievers in baseball! Perhaps the Padres have more high-leverage relievers than there are high-leverage innings to cover on a given night in the regular season, but that’s irrelevant to this trade. Rather, the final innings of every Padres playoff game will feature closer after closer after closer after closer.

This is very much a live for the moment trade. San Diego might be underwater before De Vries ever makes his major league debut. He might never make a major league debut! Prospects are volatile. Meanwhile, the Padres are good this year, and their best players are in their primes. Think of it this way: If the Padres had paid $4 million, De Vries’ reported signing bonus, for the rights to Miller last year, we’d all agree that was a coup. This isn’t quite the same, but it’s surely at least a little bit similar.

I reserve the right to adjust how I feel about this deal based on what follows. I think that Preller has another trade or two up his sleeve. Maybe the increased price of relief pitchers – hey, did you hear the A’s got a top-25 prospect for a closer?! – will lead to a Suarez deal. Until the deadline music stops, you can’t look at the Padres as a finished product. That’s not how they operate.

I’ll give them a B for now, but with huge error bars. I don’t like this trade at face value. The Padres are giving up a ton to add at the position where they’re already deepest. I like it a bit more based on what trades they might still make. I like it a bit more based on some small chance of turning Miller into a starter in the future. I like it a bit more because they’re in a win-now window and probably don’t need an 18-year-old shortstop anytime soon, though De Vries was a key trade chip that plenty of other teams probably would have wanted. I’m not sure this is the best the Padres could have gotten for him. Even so, this team is better now than it was this morning — and deadline day is a lot more fun because of it.