Aramis Ramirez is a big upgrade offensively for the Brewers at third base.
Meanwhile, Ramirez was probably the second- or third-best-hitting third baseman in the majors in 2011. Only Pablo Sandoval had a higher OPS among third basemen with at least 400 plate appearances. Putting aside Ramirez's long-term value, let's assess where the Brewers stand.
Baseball is about scoring runs and preventing runs. Let's put all this into the mixer and see what it might mean in terms of run differential for the Brewers.
It's difficult to put into words how awful McGehee was in 2011, and in retrospect, it's amazing that Ron Roenicke kept starting him until essentially the final week of the season and playoffs, when he finally inserted Jerry Hairston. Anyway, using figures from FanGraphs.com, Ramirez created about 99 park-adjusted runs in 626 plate appearances in 2011; McGehee created about 46 runs in 600 plate appearances (or 48 over 626 plate appearances). McGehee is no Gold Glover, but Ramirez plays third base about as well as a tree stump these days. Baseball Info Solutions had McGehee at minus-2 runs in defensive runs saved and Ramirez at minus-12.
Offensively, Betancourt and Gonzalez are pretty much mirror images of each other: low-OBP hackers with a little pop for shortstops. In nearly the same total of plate appearances, Betancourt created about 48 runs, Gonzalez about 50. The big difference comes on defense, where Betancourt (having a good season for him) scored at minus-6 but Gonzalez at plus-15.
Fielder hit .299/.415/.566, creating about 128 runs over his 692 plate appearances. The Bill James projections listed at FanGraphs have Gamel hitting .282/.342/.476 and creating 70 runs over 483 plate appearances. If we prorate that to 692 PAs, we get 100 runs created for Gamel. Defensively, Fielder actually rated well in 2011 at minus-1. Gamel is not regarded as a good defender. Let's call that one a wash.
Braun created 129 runs in 150 games in 2011, so he'd lose a third of that production, or 43 runs over the 50 games he would miss. Let's say a replacement-level left fielder would create about 75 runs over a season, or 25 runs over 50 games. BIS had Braun at minus-3 runs on defense, so let's call that a wash for now as well.
Add it all up, and even with the loss of Fielder and the potential loss of Braun for 50 games, we get the Brewers at plus-18 runs better than last season.
Now, there are plenty of caveats here: Ramirez might not hit quite as well as in 2011; Gonzalez might not field quite as well as in 2011; Gamel might not meet his projections. Even if Gamel does that, he's unlikely to play every game like Fielder did, and the Brewers might not get adequate production from their backups. Still, even if you downgrade the run differential for all those reasons, these moves essentially leave the Brewers spinning their wheels.
Yes, losing Fielder hurts. And it's entirely possible Gamel will struggle and not hit. But replacing McGehee's bat and Betancourt's glove are such positives that the Brewers appear to be able to absorb the loss of the big guy.