Gantner had 4.3 bWAR in his career year, 1983. He never had another season above 2.6 bWAR, and he only topped 2 bWAR four other times.
Fernando Vina wasn’t even a poor man’s Jim Gantner, with a top Brewers bWAR of 3.1 and nothing else over 1.7. Peaked at 3.2 with St. Louis in 2000.
Ronnie Belliard? Top two Brewers seasons of 3.5 and 2.4. Had his best year with Cleveland at 4.5 in 2005.
Weeks, unlike the other three, actually put up two 3-WAR seasons as a Brewer: 3.6 and 3.0.
Turang, in just three seasons, already has two — 4.7 last year, 5.5 this year — that beat any season any of those four guys ever put up.
He has already clearly eclipsed all of them, unless you want to argue that standing around for 17 years taking up space on mostly bad teams amounts to something other than mediocrity.
Molitor had the only Brewers 2b career better than Turang’s, barely — 12.1 bWAR to 11.7, both in three seasons. I don’t know what to do about 1990, when Molitor put up 3.2 bWAR in 103 games, just 60 at 2b. Turang won’t be Paul Molitor, but if he has one or two more good years, he’ll be a greater Brewers 2b than Paul Molitor was.
(Shout out to Don Money — 5.1 bWAR in his only year as a primary 2b, 1977.)