When I think of some guys who were in the Brewers Minor League System who now are with another team, the first that comes to mind is Nelson Cruz, although obviously there is Matt LaPorta and several others. However there are some brewers minor league farmhands who may have escaped your radar a bit:
Marco Scutaro is in the majors with the Red Sox at this time. He was actually the player to be named later in a big trade that sent Kane Davis, Paul Rigdon, and Richie Sexson to the Brewers on August 30th of 2000. So along with those three guys, he was sent to Milwaukee. In return for those four, the Brewers parted ways with Jason Bere, Bob Wickman and Steve Woodard. Within two years of being in the minors for the Brewers, he was placed on waivers and selected by the Mets. In his major league career, he has played 2B, 3B, SS, LF, and RF. He has a career .266 batting average with 52 HR and 36 SB in 869 games.
In the minors he has batted .289 in his career with 73 HR and 122 SB in 891 games, 136 of which were spent at AAA for the crew. He never appeared in the majors for the Brewers.
Another farmhand people may overlook is Joe Thatcher, who was shipped to the Padres for Scott Linebrink on July 25th, 2007. He never appeared in a major league game for the Brewers either, but has since gone on to a 3-6 record with a 4.12 era in 105 career major league relief appearances for the Padres. His career record in the minors is 23-15 with an impressive 1.94 ERA.
OF Freddy Parejo made his debut with the Arizona Rookie League Brewers in 2004. He spent 2004-2009 in the minors with the Brewers and now is with a single A Affiliate for the Astros. In the minors he has compiled a career .252 batting average with 18 home runs and 33 stolen bases in 557 games. He has never appeared in the majors for any team, but he is definitely a forgotten Brewers farmhand. I will have more forgotten farmhands for you next week!