What happened: Boston had offered fastball-heavy pitching prospect Payton Tolle as a centerpiece for Ketel Marte, per Alex Speier of the Boston Globe, before refusing to include shortstop prospect Marcelo Mayer. Had the swap gone through, the Arizona Diamondbacks were widely projected to fill their lineup gap by signing third baseman Alex Bregman to a five-year, $175 million contract, per Ken Rosenthal of The Athletic.

Why it matters: Bregman reportedly preferred living and playing in Arizona year-round, much like Diamondbacks starter Corbin Burnes, until Arizona's Jan. 12 acquisition of Nolan Arenado prompted Bregman to sign with the Chicago Cubs the next day. Keeping Marte also led the Diamondbacks to re-sign right-hander Zac Gallen while passing on Tolle ahead of his 2026 breakout with the Red Sox.

What to watch: Because Marte's 10-and-5 service-time rights vested in April 2026, the second baseman now holds full no-trade veto power entering the winter market.