This is really two separate trades, but I've lumped them together to show the overall plan for the Mariners. The Mariners are said to covet a RHB first baseman. Now, they can go cheap and sign someone like Justin Turner, but the wheels seem like they're about to fall off that cart. They can go BIG and sign Alonso to a long-term expensive deal, while giving up draft picks in the process, but that doesn't seem like the Mariners' move to me. Lastly, they can trade for someone like Yandy Diaz, someone who has performed as well as or better than Alonso in recent times and isn't anywhere near as expensive. So this trade sees the Mariners swapping Castillo and his $20+ million salary for Littell and his $4ish million salary, while adding Diaz (and his $10 million salary). Mariners are a lot better in 2025 as a result, while saving a few bucks in the process, but make no mistake, this is a win-now move. The prospect cost is reasonable, as they don't really need Ford with Raleigh on the team or Arroyo with all their other more highly ranked SS prospects (plus Crawford in the Show). They also add a pretty good young pitcher from the Giants who was rushed from A+ last year to the Show, but can serve as AAA depth for the Mariners in 2024 and a 3B prospect in Schmitt. Littell was just as good as Castillo last year, so there's no drop off in talent there. The Giants need another SP but there aren't really any left in free agency, so they trade for Castillo to shore up their rotation. For the Rays, they are looking ahead to 2026 and opt for high quality prospects to add to the top of their System, as they already have the deepest Farm in baseball. Everyone wins!