The move may have been a bit of a surprise, considering Proefrock signed a two-year extension with Baltimore earlier this season.
Proefrock, who served as director of baseball administration with the Orioles, was hired by Baltimore in 2005 by executive vice president Mike Flanagan and was in charge of interpreting Major League Baseball rules, as well as handling arbitration cases and other contractual matters.
"It's never easy to lose quality people, and that's what Scott was," Orioles president Andy MacPhail said in a phone interview.
"It wasn't a surprise that he got an opportunity in what he thought was an advancement of his career. Our policy is that we are not opposed to granting people permission to pursue other jobs."
MacPhail said it would likely take a while to find Proefrock's replacement, but it would definitely be done before the start of the 2009 season.
"Ideally, you'd like it to get done in a couple of weeks," MacPhail said, "but I imagine it would be a bit of a process."
Prior to coming over to the Orioles, Proefrock spent 11 years with the Rays. With Tampa Bay, he was director of baseball administration for the first year and a half (1995-96) before being named assistant general manager in January 1997 -- a position he held through the 2005 season.
Proefrock also worked in scouting and player development for the Pirates and Braves. From 1989 to 2005 -- while with the Pirates, Braves and Rays -- Proefrock worked under Chuck LaMar, the current Phillies' assistant general manager of player development and scouting.
Proefrock was chosen over former Mets GM Jim Duquette, former Reds GM Wayne Krivsky and Muzzy Jackson, formerly an assistant GM with the Royals.
"It was an honor to be asked for permission [to interview] and even greater honor to be offered the position," Proefrock was quoted as saying in The Baltimore Sun. "I was thrilled to be accepted and move forward with my career. I'm looking forward to the challenge and helping them maintain the excellence that they've achieved."
Alden Gonzalez is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.