The Athletic has live coverage of the 2026 MLB Trade Deadline.Trade details: The San Francisco Giants acquire infielder Marcelo Mayer from the Boston Red Sox for lefty reliever Erik Miller.I don’t get this one at all. Marcelo Mayer was a top-10 prospect not that long ago, and still a top 25-ish prospect before he reached the majors, and still has less than a full season’s worth of playing time in the majors. He hasn’t hit a lick, to be clear, but some of this is mechanical and could be addressed, and he’s already shown he can be an above-average second baseman or third baseman if he isn’t the above-average shortstop he appeared to be as a teenager. To trade all of that potential, even with most of it unrealized, for a left-handed reliever with good stuff and poor control in his best years seems like selling lower than low.Mayer gets crushed on off-speed stuff, which has been an issue for him since Double A. His front leg stays very stiff through contact, with his knee locked in place, and he can’t cover the lower third or anything below the zone. When he’s swung at anything below the bottom of the zone, he’s whiffed 56.5 percent of the time, and pitchers are going to keep attacking him there until he makes an adjustment — and he chases those pitches too often, too. I’m not saying this is the entire problem, but helping him move that front knee more is part of a bigger solution.I’d also love to see him get one position and stay there, probably second base at this point, but wherever it is, having him stick in one spot could at least allow him to focus on all of the changes he needs to make at the plate. As bad as he’s been in the majors, he hit .307/.370/.480 in Double A in 2024, and .271/.347/.471 in Triple A before his call-up in 2025. He’s always had raw power, which we saw in the minors but really never in the majors, and his swing seems geared to pull the ball out to right-center. I could just be looking at Mayer through the rose-colored glasses of a prospect guy, but I can’t see giving up on him this quickly and only getting a reliever in return.Erik Miller is almost beside the point here. He has a 70 slider and throws hard, but he’s never had average control and he was actually unselected in the Rule 5 draft in 2022 a month before the Philadelphia Phillies traded him to the Giants for Yunior Marte. You can find guys like Miller without giving up young players with the talent and potential upside of Mayer. I have done this long enough to know Mayer may never succeed — maybe he resists making the mechanical changes, maybe he just doesn’t pick up spin at all, maybe he keeps getting hurt as he has for most of his pro career to date. I’m saying if there’s even a 10 percent chance that he still becomes a star, I’m not making this deal. Perhaps the Red Sox think that probability is more like 0 percent. They know the player better than I do. From this outside vantage point, however, I do not understand this trade at all.Aug 3, 2026Connections: Sports EditionSpot the pattern. Connect the termsFind the hidden link between sports terms