Did the Red Sox Sell Too Low on Marcelo Mayer?
Mayer was once viewed as a prospect who would become a cornerstone in Boston. With him now gone, did the Red Sox give up on him too soon?
The Boston Red Sox capped off a busy deadline by sending former fourth-overall draft pick Marcelo Mayer to the San Francisco Giants for left-handed reliever Erik Miller.
Just a month ago, this trade seemed unlikely. But the Red Sox completely turned their season around and became buyers at the deadline. Boston needed bullpen depth for a postseason run, and acquiring Miller was their answer.
Mayer is the first member of the former “Big Three” (Roman Anthony and Kristian Campbell) to be moved, making the one-for-one swap even more surprising. Breslow made it clear with his moves at this deadline that he isn’t going to hoard prospects or young players anymore. But did Breslow sell too low on Mayer?
Last offseason, the Arizona Diamondbacks reportedly wanted Mayer and Connelly Early in a deal for Ketel Marte. But Boston refused to include Mayer, shutting those trade discussions down.
If Breslow hadn’t moved Mayer at the deadline, would Mayer have been able to bounce back and recoup his value? Would he have lived up to the hype in Boston? Or did Breslow make the right move by adding Miller to the bullpen?
All stats updated before play on August 6.
The Best Ability Is Availability
Mayer was the Red Sox’s highest draft pick ever in 2021 when he went fourth overall. Scouts viewed him as the best hitter and defender in the 2021 class, making Boston’s selection a steal at the time. Mayer even drew early comparisons to Brandon Crawford, making the trade to San Francisco seem like destiny for the native Californian.
Mayer was the Red Sox’s highest draft pick ever in 2021 when he went fourth overall. Scouts viewed him as the best hitter and defender in the 2021 class, landing Boston a steal at the time. Mayer had early comparisons to Brandon Crawford; the trade to San Francisco seems like destiny for the native Californian.
Throughout his minor league career, injuries plagued Mayer. Every one of his professional seasons has included a stint on the injured list, with most ending prematurely. Mayer has yet to play 100 games in a single professional season.
When he was on the field, Mayer showed why he was such a highly touted prospect. He showcased plus defensive abilities and a solid bat that projected for 20-plus home runs. San Francisco bought into that upside and will now see if he can become a cornerstone of its infield.
The current middle infield rotation of Andruw Monasterio, Anthony Seigler, and Nick Sogard has provided solid offense for the club during its turnaround. Along with this trio, Trevor Story is ramping up activity ahead of a rehab assignment. Franklin Arias, Just Baseball’s No. 3 prospect, has also made his way to Worcester, providing another option down the stretch.
With all of those options in place, Mayer’s value to Boston was at an all-time low. In his 114 games with the Red Sox, Mayer slashed .223/.278/.346 with seven home runs and 0.3 fWAR. At the end of the day, Mayer just couldn’t stay healthy, and ultimately, it hurt both his value and his future with Boston.
Erik Miller’s Value to the Bullpen
The Red Sox needed another arm in the bullpen, and they got just that and more with Miller. The 28-year-old lefty has put together a solid season, recording 0.3 fWAR with a 2.73 ERA across 33 innings. In July, he didn’t allow a single run over 11 innings while striking out 16. In his Red Sox debut on August 4, he struck out the only batter he faced.
Over the course of July, Boston leaned heavily on its bullpen, and adding Miller to the mix helps lessen the workload on Aroldis Chapman and Garrett Whitlock, who combined for 25 appearances during the month. Chapman and Jovani Morán were the lone left-handers in the bullpen, so adding a third in Miller should be a valuable boost down the stretch.
Miller has plenty to like when looking at his Baseball Savant page. His hard-hit rate sits at 27.4%, his whiff rate at 35.1%, and his strikeout rate at 32.2%. Even with this sea of red on his page, there are still a couple of worrisome aspects of his profile.
His chase rate is well below average at 26.3%, and his 15.4% walk rate ranks as the seventh-highest among pitchers with at least 30 innings pitched. We’ll see how that plays over the remainder of the season, but the Red Sox have shown they can help pitchers improve in that area.
When Chapman arrived in Boston in 2025, his career walk rate had never been particularly good, often ranking in the fourth percentile or worse. But in his first full season with the club, it dropped from 14.4% in 2024 to 6.6% in 2025, the biggest decrease across MLB. He hasn’t kept it quite that low this season, sitting at 10.8%, but it’s still an improvement over previous years.
Another aspect to watch is Miller’s experience as an opener in 2024. His success in that role gives Boston another option if it wants to deploy him ahead of Brayan Bello.
Bello has had an interesting season, to say the least. As a starter, he posted a 10.35 ERA across 35.2 innings with opponents hitting .365 against him. But out of the bullpen, his ERA has plummeted to 0.64 across 42 innings, with opponents hitting just .195.
It’s not out of the question to see Miller open games going forward before turning things over to Bello out of the bullpen. Both have shown they can be effective in those roles, and that versatility could end up being another reason why Craig Breslow targeted Miller at the deadline.
Was This The Right Move?
It’s too early to say whether or not the Red Sox gave up on Mayer too early. He’s a young player with plenty of potential and time ahead of him. Even with that, we can evaluate the trade for what it is right now.
The Red Sox made the right move by trading Mayer to acquire Miller. Miller fills their needs at this moment, while Mayer still carries plenty of question marks. You don’t go from being a potential centerpiece in a trade for Marte to a one-for-one trade piece for a relief pitcher without there being concerns attached to your name.
Mayer has yet to prove over the past five years that he can stay healthy and consistently produce. Even with that, he’s still just 23 years old and nowhere close to a finished product. The same can be said for Miller as well. The Giants sold high on Miller’s success this season, acquiring a former top prospect in Mayer as a key piece of their rebuild.
Boston has had the trio of Monasterio, Seigler, and Sogard provide solid middle-infield play during a time when their usual middle infielders have all been injured. While long-term this likely won’t be the answer, it’s resulted in wins so far this season. Acquiring Miller while moving an injury-prone Mayer is a move made with the goal of winning now.
The front office could also be viewing Arias as its long-term option and valuing him over Mayer. Trade rumors connected Arias to top targets Hunter Goodman and Zack Neto, but the front office chose not to move him. Arias has made a tremendous jump in power, hitting 18 home runs in the minors before this season and sitting at 22 so far this year.
Arias is a prospect just like Mayer, and this scenario could play out the same way — only time will tell. But so far, Arias hasn’t dealt with the same injury issues that have followed Mayer. When September arrives, Arias could find his way to Boston to help with their playoff push.
A month ago, a win-now deadline approach seemed unthinkable for the Red Sox. But a lot can change in a month, and Mayer now finds himself in the crossfire, looking to prove something in San Francisco.
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