As a player, he played two seasons in France, two in the USISL, one in Mexico and four in Major League Soccer, achieving his most success with the Los Angeles Galaxy and D.C. United.
He went on to play four years of college soccer at the University of Virginia under Bruce Arena[2] - an association that would serve him well in his later coaching career.
[3] His first experience abroad came at La Ciotat, in the French fifth division,[4] but a six-month battle with Hodgkin's Disease in 1993 disrupted his career and almost ended his life.
[5] His first managerial job in professional soccer came when he was hired as assistant coach to Thomas Rongen – later replaced by Ray Hudson – at D.C. United, a position he occupied from 2001 through 2002.
In 2005, Onalfo was included among the final three candidates for the top job at the Colorado Rapids, eventually being passed over for Fernando Clavijo.
He pledged to install an attacking style as a coach for the Wizards,[12] who had finished poorly in their previous season and failed to make the playoffs.
Wizards technical director Peter Vermes cited Onalfo's skill as a communicator, leadership, scouting, and talent evaluation in announcing the hire.
[13] With the Wizards in sixth place in MLS's Eastern Conference with a 5–6–7 record and coming off a 6–0 road loss to FC Dallas two nights earlier, Onalfo was dismissed on August 3, 2009.