D.C. United has been preparing all week to play tonight's match at New England without defender Ryan Nelsen and midfielder Dema Kovalenko, who departed on unique overseas assignments.

But the club's prospects became more precarious yesterday when forward Jaime Moreno, the club's most effective attacking player, said he would not be able to play against the Revolution because of a quadriceps injury.

"It's not too bad, but you have to be careful because you don't want to make it worse," United's leading scorer, with two goals and three assists, said while watching practice at the RFK Stadium auxiliary field with ice wrapped around his right leg.

Not all the news was grim, however. Midfielders Bobby Convey and Ben Olsen seem set to return to the starting lineup after missing three and two games, respectively, with leg injuries. They will compensate, to some extent, for the loss of Moreno, who holds the ball and passes under pressure better than anyone on the team.

Moreno, who has played all but 69 minutes this year following offseason back surgery, was injured during a shooting drill at Wednesday's training session and hasn't practiced since. He said he hopes to be ready for the June 5 match at Chicago.

"We're up to the challenges," Coach Peter Nowak said. "The team is ready. We have 16 healthy players, and we're going to play hard. That's all we can do."

United's defense will be tested again without Nelsen, who missed the past two games because of a groin injury and is now in Australia with New Zealand's national team for the start of 2006 World Cup qualifying. (He will also miss next weekend's MLS match.) In Nelsen's absence, United (2-4-3) yielded six goals in losses to Los Angeles (4-2) and Colorado (2-1).

Kovalenko's departure to Barcelona to participate in a tribute match for former Spanish league and MLS star Hristo Stoitchkov further depletes United's defensive unit. Nowak was under no obligation to release Kovalenko for the exhibition in the middle of the MLS season, but he said it was a "once-in-a-lifetime opportunity" that his Ukrainian defensive midfielder shouldn't miss.

"We're going to adjust the situation but I think we have enough good guys to cover for us," Nowak said.

United has missed Olsen's energy in central midfield, and with Moreno sidelined, he will inherit more playmaking responsibilities.

"I feel pretty good," Olsen said. "It's amazing what two weeks off will do for you. . . . We have some key guys out and we're going to really have to stay organized and defend and communicate. Without Jaime in there holding the ball and keeping it from them, we'll have to do some good defending and match their fight and then hopefully sneak a goal or two."

Nowak is expected to start three rookies tonight: forward Freddy Adu (two goals, one assist), midfielder Josh Gros (one goal, two assists) and goalkeeper Troy Perkins, who made his MLS debut last weekend in Denver. Nick Rimando, who has started seven of nine games in goal, will also make the trip, but Doug Warren, the longtime No. 2 keeper, was left behind.

United Notes: The club announced that its July 14 exhibition against Nottingham Forest at RFK Stadium will be preceded by a game between the English club's women's squad and players from the old Washington Freedom. It's unclear whether U.S. national team stars Mia Hamm and Abby Wambach, who are preparing for the Olympics, will be available for the Freedom. . . .

A representative for Ghana's Nana Kuffour said he will travel to Africa this weekend in an attempt to finalize the rookie midfielder's visa and international clearance issues -- the final steps before his signing can be formally announced. Kuffour reached a contract agreement three weeks ago. . . .

New England (1-3-3) will be without defenders Carlos Llamosa (knee) and Rusty Pierce (quadriceps) and forward Joe-Max Moore (knee). . . . The Revolution is anticipating a crowd of about 20,000 for Adu's first appearance in Foxboro. The team is averaging 13,374.