Washington, D.C. (Sports Network) - D.C. United forward and assistant coach Josh Wolff had surgery to repair a herniated disc and will be sidelined for an undisclosed period, the club announced Tuesday.

Wolff, 35, had the surgery Monday and "the timeframe of his return is unknown at this point," according to the club. He has played nine games, including one start, this season.

The ex-U.S. international was on the 2002 and 2006 World Cup teams, and played 52 times for his country. He has played in MLS since 1998, and was named an assistant under United head coach Ben Olsen this season.

The Sports Network