The Brewers have clinched the NL Central division and basically have nothing to play for this weekend during their final regular season series against the New York Mets. They're already locked into the 3rd seed, having to host a best-of-three game Wild Card series starting on October 1st.
As for the Mets, they are still fighting to get in the playoffs, potentially facing the Brewers again if they end up grabbing the 3rd Wild Card spot. To start the regular season, the Brewers swept the Mets in New York.
The New York Mets could not play the last two games of their series against the Atlanta Braves earlier this week, making this series more important for them. The Mets are scheduled to play a doubleheader in Atlanta on Monday, a day before the Wild Card series begins if they were to make the playoffs. That has huge implications if New York plays the Brewers. They would be a tired team with a burnt-out rotation and bullpen.
The Mets could possibly play three games in Milwaukee, fly back to Atlanta to play a double-header, then have to fly back to Milwaukee to start the best-of-three Wild Card. In order to earn that postseason spot, they're going to have to expend a lot of energy on that pitching staff just to make it. The Brewers, meanwhile, can have a clear impact on who their potential postseason opponent would be. Beating the Mets could kick them out of the playoffs, losing to them could mean the Brewers would have to play them again.
As for the starting pitchers for this series, Frankie Montas will be starting on Friday but the other two starters are TBD as things stand right now. Milwaukee could possibly bring up Carlos Rodriguez, who is reportedly with the team on the taxi squad, or go with a committee since they would like to keep their main arms fresh for the playoffs.
New York will have Sean Manaea start this Friday who has been lights out this season for New York. David Peterson will likely be starting on Saturday and then Luis Severino possibly on Sunday in the series finale. Mets manager Carlos Mendoza has yet to officially announce starters for the last two games but that is the likely route that he will take.
There could possibly be some tension in this series dating back to the regular season when Rhys Hoskins and Jeff McNeil had an altercation that led to both teams coming on the field. McNeil has been on the IL for a couple of weeks now but that doesn't keep anyone from chirping away.