The Mets can't win because the Brewers bullpen is well-rested and in better shape entering this series.
The Mets used virtually all their high leverage relievers in Monday's game and given that Edwin Diaz threw a whopping 66 pitches in the last two days, he might not be available for Game 1. It wil be a patchwork task that Mets skipper Carlos Mendoza must try to finish games.
Meanwhile, for the Brewers, they last used their high leverage relievers on Saturday, so they come in with two days of rest. And their unit as a hole has been exceptional all year. Their bullpen ranked 2nd in ERA and 3rd in WHIP this season, and they've been instrumental in getting the Brewers to where they are. They'll be able to chose from Joel Payamps, Aaron Ashby, Jared Koenig, Trevor Megill, and Devin Williams. Williams missed the first four months of the season due to injury, but has posted a 1.25 ERA in 21.2 innings pitched this season.
The Mets can win because they have so much momentum to carry over into this series.
The Mets have been used to playing intense, edge-of-your-seat baseball games for weeks now just to get into the playoffs, and they emerge from the end of the season as a confident ballclub that had to be the best team in baseball over the past four months just to get into the playoffs. The Mets overcame so much adversity all season long and they have proven to be mentally tougher as the season progressed. As a result, the Mets have nothing to lose and have a track record of success, thanks to the steady leadership of Carlos Mendoza.
Meanwhile, the Brewers ran away with the NL Central and had their seed locked in for a week now, meaning their recent games have been used to determine and construct their roster for the playoffs. The Brewers were not expected to make the playoffs, either, given they lost ace Corbin Burnes and star manager Craig Counsell this offseason. However, nobody thought they would win the division by 10 games. Some potential rust could be an issue there.