It may be a little early to revisit this trade. But roughly 100 games in, things are not looking good. This trade was a bad contract for a bad contract. It was just a matter of who's going to beat the aging curve.
2026 Numbers:
Brandon Nimmo. .764 OPS. 2.0 WAR.
Marcus Semien. .607 OPS. -0.8 WAR.
Nimmo isn't an All-Star, but those numbers aren't terrible for $20M. He would have been one of the best hitters in the Mets lineup. Meanwhile, Semien is shot. He failed to put up numbers even as good as last year, and now his defense is gone as well.
So let's assume this is Nimmo's last productive year. Starting next year, he will have 4 years, $82M remaining on his contract. The Mets threw in $6M, so the total money they'd have to eat is $76M, spread out over the next four years.
The Mets, on the other hand, took on Semien with 3 years, $72M left on his contract. Semien was terrible, so the Mets are basically eating that entire contract. Plus, they took on that additional $6M, so that brings the total to $78M. $78M over three years, versus $76M over four years. Safe to say the Mets already lost this trade.
If Nimmo continues his production through next year, or even through 2028, then the deal gets even worse for the Mets. In hindsight, the better play would have been to retain Nimmo, not sign Polanco, and let Brandon be the DH/1B. I get that we have no idea of Brandon can play 1B, but we're in August, and we still don't know if Polanco can either.