FanGraphs projects the Brewers rotation for 11.9 WAR this year. Last year they posted 11.2 FIP based WAR which only takes into account their K, BB, HR and IFFB numbers. Once the defense (+68 DRS, 2nd in MLB) entered the equation, they came out at 15.8 runs allowed based WAR.
By that math, the rotation projects around four wins or so worse than last year. And that is with a projected 4.39 FIP/4.22 ERA (-0.17) for the group. Last year that FIP/ERA gap for the starters was over twice as large at 4.34 FIP/3.94 ERA (-0.40). If the defense works their magic again that would mitigate things even more.
If the offense improves to mediocre and puts up an even 100 wRC+ that would be an improvement of 61.4 batting runs, or about six wins, from what they contributed last year with a 92 wRC+.
The bullpen is unlikely to repeat their historic performance (+11.73 WPA), but if they are able to come in around 2018 (+5.65 WPA), 2019 (+5.22 WPA) or 2021 (+5.90 WPA) levels that would shave say another six wins off of last year.
So essentially the math is something like 90 pythag wins in 2023, minus 4 wins from SP, minus 6 wins from RP and plus 6 wins from offense comes in around 86 wins in 2024.