[1][2] At Ashbrook, Armstrong was a punter and wide receiver on the football team and began playing basketball as a senior.

[4] In 1988, Armstrong joined the Fayetteville State basketball team and would play three seasons under coach Jeff Capel II.

[4][5] Armstrong was not selected in the 1991 NBA draft and began his career with the Atlanta Eagles (renamed Trojans in 1994) of the United States Basketball League (USBL) in 1991.

[8] Armstrong later played for the South Georgia Blues of the Global Basketball Association until the team folded in 1993.

He volunteered at Ashbrook High School as an assistant basketball coach and worked the night shift at a yarn factory.

[11] For the 1994–95 season, Armstrong played for Coren Ourense of the Spanish Liga ACB and averaged 24.6 points, 4.5 rebounds, and 2.5 assists.

[4][10] Armstrong first signed with the NBA as a free agent for the Orlando Magic in late 1994–95, playing in the last 3 games of the regular season with 10 points in 8 minutes of action including a spectacular one-handed reverse windmill dunk late in a blowout vs the Indiana Pacers in his 2nd game.

He was traded by the Hornets to the Dallas Mavericks in exchange for Dan Dickau and a second round draft pick on December 3, 2004.

[14] After appearing in the 2006 NBA Finals with the Mavericks, he was traded to the Indiana Pacers in exchange for guard Anthony Johnson in July 2006.