Josh Naylor, Cleveland Guardians
Of the players I'm listing here, Naylor is the one true legit big bat who will likely also bring the heaviest price of a top prospect and possibly a player on the current San Diego big league roster.
The one-time Padre is batting .308 with 15 homers and 79 RBI and is batting .344 this month after hitting .370 in June. Naylor is Cleveland's primary first baseman, but does frequently serve as their designated hitter as he's had 89 at bats in that role carrying a .270 average. Cleveland just traded their last true quality starter Aaron Civale to Tampa Bay, so although just a half-game behind Minnesota for the AL Central lead, the Guardians front office may be thinking what everyone else already believes to be true, "whether its Cleveland or the Twins, not much is going to happen for the AL Central this postseason."
Not only would Naylor be a huge upgrade at first base and designated hitter, but he'd automatically be one of the best offensive weapons on the Padres roster. Naylor is on his second one-year, arbitration-avoiding contract with Cleveland so this could turn out to be just a rental, but hey, they're going for it. Right?!
A quick note before going shopping for the Josh Naylor statue materials: as great as the past two months have been for Naylor at the plate, over his career he's a career .247 hitter in August and .238 in September/October.