D.C. United all-star defender Ryan Nelsen has flown to Milwaukee to see a specialist for the second time this year about his groin and abdominal muscle ailments and to determine whether he will need surgery for a sports hernia, club officials said yesterday.

"That's obviously the worst-case scenario," United President Kevin Payne said of the possibility of a hernia. "If that's not the problem, we're hoping he could rehab it and get back on the field after the all-star break."

Nelsen has played in only 11 of 18 regular season games and missed three nonleague matches, primarily because of his various injuries. He didn't travel with the team to Dallas for the 5-1 loss to the Burn this past Saturday and already has been scratched from the MLS All-Star Game, which will be held this weekend at RFK Stadium.

Nelsen suffered groin and abdominal injuries several weeks ago and was having knee problems. His recovery seemed to be going well, but "things flared up and we felt he should get it checked again," Payne said.

"It's been getting progressively worse," United technical director Dave Kasper said. Surgery would likely sideline Nelsen for at least six weeks. Otherwise, he would probably need two weeks to recover. Kasper and Payne said they expect to learn the diagnosis and prognosis today.

An all-star selection the past two seasons, Nelsen and outside back Bryan Namoff are the only two United defenders who have played consistently well this year. Nelsen's absence has left United's central defense vulnerable to opposing strikers, and with veteran Mike Petke and second-year player David Stokes struggling, D.C. (5-7-6) has had problems protecting goalkeeper Troy Perkins.

Besides Nelsen, defender Brandon Prideaux and midfielders Ben Olsen and Earnie Stewart were sidelined with injuries last week. Prideaux hurt his hamstring and Olsen, who strained his quadriceps scoring a goal three weeks ago, is questionable for the All-Star Game. Stewart, who has missed the past two league games with a pulled groin, was given a week off to recover and visit family in Europe.

Petke left the Dallas game with a leg strain and midfielder Nana Kuffour has been slowed by an ankle problem.

Club officials hope those players will be able to accompany the team to San Jose for its match Aug. 7.

Injured attackers Santino Quaranta, Eliseo Quintanilla and Thiago Martins have yet to play in a league match this year, with only Quaranta in the team's immediate plans.

United Notes: The team's parade of tryouts continued with three invitees: Trinidad and Tobago midfielder Addae Rique, who has been playing for the St. Louis Steamers in the Major Indoor Soccer League; defender Kevin Taylor, a 2004 third-round draft pick by Colorado; and forward Uche Chinyere, a Jamaican-based Nigerian. However, "there were no answers there," Payne said. "We'll keep looking."

-- Steven Goff

D.C. United all-star defender Ryan Nelsen has played in just 11 of 18 league matches because of injuries.