2. Aaron Civale
This might be a surprise to some, but if we're just looking at the initial playoff roster which will likely be the Wild Card round, that's only a best of three series. The Brewers only need to carry three starting pitchers, they don't need all five. Playoff rotations also usually shrink down to four starters once you get beyond the first round.
This doesn't mean Civale isn't going to make any postseason roster, should the Brewers advance past the first round this year. Civale has been better since coming over to the Brewers, pitching to a 3.84 ERA with the Crew as opposed to a 5.07 ERA with Tampa Bay.
When you project the Brewers rotation for a best of three Wild Card round, who are their three best starters right now? You're looking at Freddy Peralta likely starting Game 1, then after that Frankie Montas and Tobias Myers have been the Brewers best starters down the stretch. They are likely to earn those starts over Civale based on performance.
That leaves Colin Rea and Aaron Civale from the current rotation that are unlikely to earn starts in the first round. It feels likely that one of those two will still make the roster but in a bullpen capacity, perhaps jumping in if one of the starters runs into trouble. Rea has started to get some work out of the bullpen between his starts and seems to be getting primed for a bullpen role. He has that experience while Civale doesn't.
Civale last pitched on Saturday and is slated to pitch on Thursday against the Pirates. On regular rest, he'd line up for Game 2 as he's right behind Freddy Peralta, but just because he's right after Peralta during the final week of the regular season doesn't mean the Brewers are going to go with him for Game 2 behind Peralta in the postseason.
Civale has a 4.12 ERA in his four September starts and has made it past the fifth inning just one time, going 5.1 IP against the Giants. He hasn't been one of their top starters lately and that could keep him out of the Wild Card. Should the Brewers advance to the NLDS, he absolutely could return, however.