If the Padres win today, then get 2 full days off to line up their starters better plus have a rested back end of the bullpen, that advantage isn't that great - you'd assume they view game 1 against the Miz as a "who cares who we start" game, thinking if it's somehow tight late their high leverage relievers give them a good shot at stealing game 1. If Miz is on and the Brewers score enough early, they're going to gun for trying to win game 2 and then hope the Brewers' starting pitching weakness for games 3 and 4 on the road wind up not bringing the series back to Milwaukee.
I'd much rather have the Cubs scratch out a W today and then have both teams empty the pitching tanks tomorrow, take out an extra travel/rest day for the Padres, and have either the Padres or the Cubs wondering how they're going to piece together a competitive starting rotation without constantly having arms on short rest this weekend.