The system most often used for determining if a team is getting lucky or playing well is to compare actual record against a projection of wins based on run differential. This is generally based upon Bill James Pythagorean Equation.
According to this type of equation the Brewers should have 33 wins and the Cubs should have 35 wins so far this year. In essence this says that over a given year a team’s win/loss record will even out based upon runs scored vs. runs allowed.
I believe this theory inaccurately values each run equally. I also believe that Stearns has figured this out. When a baseball game begins, each team has certain percentage likelihood of winning the game based upon the starting pitcher, who has the day off, individual team skill… As one team gets a lead their win percentage naturally increases.
So the Pythagorean Equation value of runs scored and runs allowed should also change within a baseball game. Once having a lead, preventing runs against has a higher impact on whether the leading team wins. As the Brewers have shown a lower runs allowed while having a two run lead has led to them to not losing any of these games.
Taken at its extreme, a team that never allows a run when having a lead that also allows ten runs a game when it falls behind could out win its stable Pythagorean Equation by twenty games if it gets a lead in 55% of its games.
So while national pundits are saying the Brewers are getting lucky by winning more than they should and things will balance out; this may not come to pass. Josh Hader and the length of the bullpen changes this equation. And provide for the opportunity for the Brewers to significantly out win the expectation by six to nine games. That is the difference between winning 86 and winning 95 games this year. That is the difference between the Brewers winning the division and the Cubs winning the division.