The 2012 Brewers were dead last in the big leagues in bullpen ERA. One might expect that sort of thing to lead to changes, and indeed it has: of the seven men who appeared in 30 or more games for the Brewers last season -- Francisco Rodriguez, John Axford, Kameron Loe, Jose Veras, Manny Parra, Tim Dillard, and Jim Henderson -- only Axford and Henderson are still around. In place of the others are newcomers Burke Badenhop, Mike Gonzalez and Tom Gorzelanny, with returning Brewers and farmhands Brandon Kintzler, Josh Stinson, Johnny Hellweg and Michael Olmstead to fight over the remaining spots. So that's different, certainly. But how much of a difference will it make?
The 2012 squad's bullpen was probably not quite as bad as it looked, for one thing. Brewers relievers were 22nd out of 30 in FIP and were actually seventh-best in baseball in xFIP, meaning that when luck and defense are removed (that's what FIP tries to do), the bullpen ended up looking merely mediocre rather than awful. If you add in the idea that pitchers don't have a ton of control over whether a fly ball to the outfield becomes a home run (that's the xFIP concept), it ends up looking downright good. There were a lot of ugly ERAs in the Brewers' bullpen, but none (well, maybe Livan Hernandez, who pitched just 36 ⅓ innings over 26 games) looked too terrible if you focus on their underlying numbers. Parra put up a 5.06 ERA, but a 3.62 FIP; Loe had a 4.61 ERA, but a 3.57 xFIP. It's doubtful the bullpen was as good as xFIP makes it look, but it probably wasn't entirely terrible, either -- there was probably some serious bad luck at work.
That said, the new guys certainly feel like an improvement. Badenhop has been a dependably effective middle reliever through each of his four full years, certainly more reliable than Parra was. Gorzelanny did quite well in his first try as a full-time reliever -- though the peripherals weren't exactly thrilling -- and has always had a great deal of talent; I'd rather have him than, say, Loe. Gonzalez was one of the best relievers in the game as recently as 2009, and while he's been hampered by injuries ever since, he seemed to have a lot of his stuff back in a 36-inning sample in Washington last season. They may stand to gain a lot from giving a bigger role to Henderson, after he struck out nearly a batter and a half per inning in his 30 ⅔ last season; he won't likely do that again, but he definitely seems to fit in well as a late-inning reliever. The last few spots on the bullpen could be ugly, but if you're using those guys, things are usually ugly already.
So the Brewers' 2013 bullpen figures to be better than 2012's after all the moves, but it also figured to be better before all the moves. The 2013 squad is probably more talented than its immediate predecessor, but the edge in talent is probably small enough that it could easily be swallowed up by the random fluctuations that strike most relief pitchers' numbers every year.
And it's not likely to move the needle much in the National League Central. The division last year, as you probably know, was decided by nine games, with the Brewers a further five games behind the wildcard Cardinals. By the imperfect but convenient measure of Fangraphs' WAR, the Brewers' bullpen was worth approximately two wins above replacement, 25th in the majors, but still just five and a half wins behind the first-place Royals' ‘pen. If you don't think the Brewers have done enough to vault themselves from having one of the worst bullpens in the league to one of the very best, then they probably haven't made a huge stride forward in the standings. But every little bit helps, of course.
At the end of the day, after all these moves, the real difference-maker could be one of the only pieces that stayed put: closer Axford struck batters out at a career-high rate last year, but also walked more than he ever had, and gave up a home run nearly three times as often as he had in 2011. If he can rein it in a bit and return to his 2010-2011 levels, that's likely an extra two to three wins for the team by itself (two per Fangraphs' WAR, a bit over three if you look at Baseball-Reference), and that plus marginal improvements across the rest of the staff could really start to make an impact on the team's chances as a whole. They've rearranged the furniture all around him, but it's the big guy for the ninth inning who could (as much as a reliever can) really help shape the team's fortunes in 2013.