D.C. United midfielder Bobby Convey could be sidelined several weeks with a hamstring injury suffered in the first half of last Saturday's match against the Columbus Crew, Coach Peter Nowak said yesterday.

Nowak said the best-case scenario is for Convey to be available for the May 29 game at New England and no later than June 5 at Chicago.

Club officials are holding out hope that Convey will recover sooner, but it seems almost certain he will miss this weekend's match against Kansas City at RFK Stadium and the May 22 game at Colorado.

"We have to check it out again," Nowak said. "We're going to do everything we can to bring him back as soon as we can. . . .

"Bobby's a big part of this team. What he's bringing to the table is his speed, his ability to moving forward, backward, changing position -- this is our game when everyone is [moving] around. We're going to miss him, that's for sure, but we're going to try to cover for him."

Nowak, who played in Europe for many years, said he plans to contact hamstring specialists in Europe and will consider sending Convey there for treatment. He said he received such treatment at one point in his career and it helped him return in five days.

Convey, in his fifth season, has started all six games this year and has one assist. He also has become a U.S. national team regular, but if the injury sidelines him for an extended period, he would probably miss 2006 World Cup qualifiers against Grenada on June 13 and 20.

Convey injured his left hamstring while making a long run along the left sideline midway through the first half last Saturday.

He was replaced by rookie Josh Gros, who has played in every game (one start) and has two assists.

If Convey is out, Gros could get the starting nod or Nowak could alter his midfield lineup and add another forward.

Adu on Adu

Freddy Adu gave himself low marks for his starting performance against the Crew.

"Not too good," the 14-year-old forward said yesterday, reflecting on his 60 minutes during the 1-1 tie at RFK. He also said he might've underestimated the level of difficulty playing in MLS. "I'm playing catch-up now. . . . I'm getting closer and closer, but I'm not there yet."

This week Nowak could change his forward line, perhaps inserting Salvadoran veteran Ronald Cerritos (who has yet to start this year) alongside Jaime Moreno. However, Adu and Alecko Eskandarian also remain in contention.

Commenting on Adu's future playing time, Nowak said, "He needs experience, and experience comes with minutes." . . .

Cerritos has turned down an invitation from the Salvadoran national team to play in a friendly against Haiti tonight in Houston. He played for El Salvador against Colombia two weeks ago at RFK, but decided to skip this one in order to focus on United.

Team officials are also awaiting word on whether Moreno will be called up to the Bolivian national team for World Cup qualifiers against Paraguay and Ecuador in early June.

If he is, he would probably miss two MLS games. Defender Ryan Nelsen will miss those same two matches (May 29 and June 5) for the start of New Zealand's World Cup qualifying. . . .

Gros was excused from practice yesterday to return to Rutgers University, where he is close to finishing his course work. He is expected back in Washington today. . . .

Midfielder Yusef Sindeh, a refugee from war-torn Sierra Leone, was given a tryout by the club yesterday but was not invited back. Sindeh, 20, is attending an alternative high school in Alexandria.