Richie Williams’s tenure as head coach of D.C. United’s new second-division team lasted less than half the season.

Williams, a former D.C. midfielder who accepted the job in January, said Friday he is leaving Loudoun United to join Bruce Arena’s staff at the New England Revolution, effective immediately.

Because Williams is under contract, United will receive unspecified compensation.

Williams and Arena have a long history, starting at the University of Virginia in the 1980s and continuing in MLS and the U.S. national team. Arena last week was appointed New England coach last week and has begun building his staff.

Curt Onalfo, a former D.C. player, assistant and head coach who also has deep ties with Arena, is expected to become New England’s technical director. He is currently working with the U.S. under-20 national team at the U-20 World Cup in Poland.

Williams told his players of his departure Friday. Loudoun is 2-4-3 in its inaugural season and will not play again until June 5. Assistant Gus Teren, who has worked for the D.C. organization since 2014 as a youth academy coach, is likely to become the interim boss.

Loudoun United, a developmental platform for D.C. prospects, is playing home matches at Audi Field until a 5,000-seat stadium in Leesburg opens in August.

Williams is the second figure to leave for a bigger opportunity after a brief stay in Washington: Dane Murphy, D.C. technical director who was hired in the fall and oversaw Loudoun’s roster, departed before the season started to pursue a high-ranking job in England.

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