He noted that the Royals' outfield now features Jose Guillen, Mark Teahen, David DeJesus and Joey Gathright. Brown was being squeezed out, especially since the signing of Guillen last week.
"It was a difficult decision, but ultimately, Emil was going to have to be a part-time player and the way we were set up, other players seemed more suited to a part-time role," Moore said. "Emil needs to play every day."
Last year Brown made $3.45 million and is eligible for salary arbitration, which usually results in a sizable increase.
Brown did not play every day in 2007, even though he led the Royals with 86 and 81 RBIs the previous two seasons. In the 2005 and '06 seasons, he banged 17 and 15 home runs, respectively.
Last season, he got into just 113 games and had six home runs but still led the run-deprived Royals with 62 RBIs. He averaged one RBI for every 5.9 at-bats, his best mark in his three years with the club.
Brown started just 90 games and shared left field with several players, most notably the speedy Gathright, a .307 hitter.
Brown, who will turn 33 on Dec. 29, batted .279 in his three seasons with the Royals with 38 home runs and 229 RBIs in 410 games.
After playing parts of five seasons for the Pittsburgh Pirates, Brown was traded to the San Diego Padres in 2001. But he didn't play in the Majors for the next three years, finally making the Royals as a non-roster player in the spring of 2005.
Moore said that Brown would be the Royals' only non-tendered player. The roster stands at 39, one under the limit.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.