Cody Bellinger to the Blue Jays
While the Blue Jays are not in the Mariners division, this one could prove to be a real dagger. The Blue Jays were reportedly in late stage talks with Shohei Ohtani, so they obviously have no issue adding to the payroll. With a rotation already featuring Gausman, Berrios, Chris Bassit, and Kikuchi, they have a solid staff. Adding a bat like Bellinger to an already potent lineup featuring Bichette, Vlad, and other dangerous hitters could be the nail in the Mariners coffin.
The Mariners will be fighting for a wild card berth, and hopefully a division title. The team that finished 1 game ahead of them in the wild card was the Toronto Blue Jays. Bellinger would most certainly add a win or 2 to this team and cost the Mariners a few spots, especially if they aren't willing to spend to compete.
The best-case scenario for the Mariners, in regard to the Bellinger sweepstakes, is that he returns to the Chicago Cubs. Really, him going to any team in the National League would be a huge win for the Mariners as he would have little impact on their opportunity to make it to the postseason.