D.C. United defender Jed Zayner, who began the MLS season as the starting right back and has been sidelined by a series of injuries, will have surgery on his left knee Friday and miss between six weeks and six months, club officials said Thursday.

Zayner, 26, was injured in practice this week and placed on crutches. Tests revealed meniscus damage. If a full repair is required during surgery, he would probably miss four to six months. Under the best-case scenario, doctors would only have to do minor work, allowing him to return in six weeks.

Due to two separate hamstring injuries, Zayner has appeared in just four league matches.

For additional details.....

His absence is another setback to a young backline. Marc Burch (hamstring) and Dejan Jakovic (hamstring) have missed significant time, and Devon McTavish (concussion) hasn’t been available this season. On Wednesday, starting left back Daniel Woolard hurt his back.

United bolstered the roster Monday by acquiring center back Brandon McDonald from the San Jose Earthquakes. Adrian Reid, a center back for Jamaica’s national team, is currently on trial with United and scheduled to play in Sunday’s reserve match. His rights are owned by Portmore United in Jamaica.