Musser was drafted by the New York Mets in the second round (73rd overall) of the 1999 Major League Baseball draft.[1] He was signed on June 23, 1999.[2] After spending six years in the Mets organization, he was granted free agency on October 15, 2005.[3]
On January 30, 2006, Musser signed as a free agent with the Arizona Diamondbacks. On May 23, 2006, he was released by the Diamondbacks.[3] A day after his release, he signed as a free agent with the Kansas City Royals.[4] On October 15, 2006, he was granted free agency.[3] On November 20, 2006, he re-signed with the Royals.[3]
Musser was optioned to the Triple-AOmaha Royals to begin the 2007 season.[5] He was recalled to the majors for the first time on April 20,[6] and made his major league debut the next day against the Minnesota Twins, allowing two hits and an unearned run in 1⁄3 of an inning.[7] After making two appearances, Musser was optioned to Omaha on April 24.[8] Overall, Musser was 0–1 with a 4.38 ERA in 17 relief appearances with Kansas City,[3] and went 4–1 with eight saves and a miniscule 0.49 ERA in 32 games with Omaha.[9]
Musser made a single appearance for the Royals in 2008, tossing a scoreless inning in a 5–1 loss to the Twins.[10] He spent the majority of the season with Triple-A Omaha, going 3–5 with six saves and a 4.34 ERA in 37 games (three starts).[9]