D.C. United's disciplinary problems started Aug. 20 when Bryan Namoff was ejected for dissent. Four days later Dema Kovalenko was tossed for a mild confrontation. Another three days passed before Kovalenko received another red card, this one for an inappropriate tackle.

The next game, Josh Gros collected a yellow card, pushing him over the league-mandated limit and drawing a suspension from the following match.

And then on Saturday, during a 1-0 loss at Colorado, the usually mild-mannered Jaime Moreno was red-carded for retaliation and Ben Olsen surpassed the yellow-card limit, which means both will miss this weekend's match at Dallas.

United has had to play short-handed in almost every game for three weeks. The club is still on target to make the MLS playoffs, but three losses in the last four league games and four in the last five overall have slowed the momentum.

"The players are pretty frustrated because I think they're confused about what is permissible and what's not," said United President Kevin Payne, who has complained to officiating supervisors about calls against his team.

"Players like to have a sense of which referees are going to call the game in which ways. Too often in our league it's impossible to predict how the game is going to be called. We really don't have a sense of what's going on."

Moreno, the MLS goals leader with 12, was ejected in the second half at Colorado after tripping Rapids defender Hunter Freeman from behind after Freeman was called for fouling Moreno at midfield. "That's not a red card -- it was like tripping someone in the lunch line at school," said a team official, who didn't want his name used for fear of being fined by MLS.

United is seventh in the 12-team league in yellow cards (1.8 per game) but tied for second with Colorado in red cards (five). A sixth red card came last month in a U.S. Open Cup game.

"If you deserve a red card, there is no question and you walk away," Kovalenko said. "But some of the cards we're getting, it's disappointing. We just have to deal with it, get stronger and be smarter."

Despite his anger with some of the calls, Payne didn't excuse his players for the game results.

"Every one of those games we should have won, regardless of the [officiating] decisions," he said. "I'm disappointed our group is not finding ways to win these games. We've got to get ourselves refocused. We believe we can be the best team in the league again, but right now we're not getting the job done."

Stokes Out for the Season

Defender David Stokes, a Dumfries native who hasn't played since July 9 because of an ankle injury, will undergo surgery tomorrow and miss the remainder of the season, club officials confirmed.

United will be able to replace Stokes on the roster but won't receive any salary cap relief. Stokes, 23, had made 10 appearances and three starts in league play.

The club might also have to make a decision by the Sept. 15 roster deadline about forward Alecko Eskandarian, who has been out since mid-June with complications from a concussion.

He is scheduled to resume light workouts this week to determine whether his headaches have subsided during physical exertion. . . .

Dutch goalkeeper Jordy Schoute, 19, began an informal tryout upon his request. He had been playing for Roosendaal in the Netherlands. . . .

The club is considering signing midfielder Stephen deRoux (High Point High School, Prince George's Community College) to a developmental contract and upgrading forward Jamil Walker to the senior roster. . . .

Midfielder Clyde Simms, Olsen's likely replacement Saturday, missed practice with an illness.