I believe the Dbacks are our most likely opponent at this point. They're in a virtual tie with the Marlins due to the Marlins' likely W in NY and the Marlins hold the tiebreaker. Not to mention they face a desperate Astros team while the Marlins get the Pirates. Which wouldn't be the worst thing imo considering Gallen is unavailable for Game 1, the most important game of the series.
Reds aren't dead either. If they win these last two vs. the Cardinals, who have checked out as we all know, and the Astros do the same to the Dbacks, they're in and come to Milwaukee.