For the first time in a mostly exceptional MLS career, D.C. United defender Mike Petke has found himself sitting on the bench because of a slip in his play.

"I was saying to my wife the other day, maybe this is a good thing," said Petke, in his second season with United and seventh in the league. "I've never really been challenged like this. I'm not happy about it, but it can only motivate me and now we're going to see what kind of player I am."

Petke, 28, has been among MLS's most enduring players, averaging almost 26 starts since his arrival from Southern Connecticut State in 1998. Except for one or two instances early in his career, the only time he sat out was because of injury or suspension. But after playing every minute of United's first four matches this year, Petke was replaced by veteran Brandon Prideaux.

Coach Peter Nowak wouldn't get into specifics of Petke's benching and Petke didn't want to share the discussions he has had with the coaching staff about the decision, but the move has not caused any noticeable friction between the no-nonsense coach and the notoriously outspoken defender.

"There's no ill will, whatsoever," said Petke, a mainstay for the New York/New Jersey MetroStars until he was traded to United prior to the 2003 season. "The one good thing I can take from this, I've known players over the years who have been benched and not a word has been said to them. [The United coaching staff] has been up front with me and honest with me and I appreciate that. I know what I have to do."

Prideaux earned good reviews from Nowak in the last two matches (1-1 ties with San Jose and Columbus) and will likely keep his starting job for Saturday night's game against the Kansas City Wizards at RFK Stadium. But Petke is almost certain to return to the lineup in a few weeks, if not earlier, when team captain Ryan Nelsen, a central defender, departs for New Zealand national team duty.

United's other defenders are Bryan Namoff, who has started every game; and second-year player David Stokes, who has yet to make an MLS start.

"Peter has a very difficult decision," Petke said. "I think Brandon is a very good player; I think Brandon should be on the field. I think Bryan should be on the field, I think Ryan should be on the field, I think I should be on the field. But it just doesn't work that way. I'm just going to keep working harder."

Said Nowak: "Mike is a guy who is not going to stop -- he's going to work his way back. This is competition."

United Notes: Nowak ($500) and midfielder Ben Olsen ($250) were fined by MLS for comments they made about the officiating last weekend. . . .

Midfielder Bobby Convey will not be sent to Europe for treatment of his hamstring injury, technical director Dave Kasper said. Nowak had considered sending him there to see specialists. . . .

Forward Jaime Moreno was not included on Bolivia's roster for upcoming World Cup qualifiers. United had feared he would be called up and have to miss two MLS games. . . .

A D.C. game at Dallas has been moved from July 31 to July 24 to accommodate the new date of the MLS All-Star Game. The Post reported last month that Real Madrid has tentatively agreed to play the MLS all-stars in Foxboro, Mass. . . . The Northern Virginia Royals, a local minor league team with informal ties to United, will hold tryouts next week in Herndon. For information, call 703-490-4988.