Through the first five months of his rookie season, D.C. United's Bobby Boswell had played every minute of every match for which he was available. He had anchored an evolving back line, scored a late game-winning goal against Chicago and provided his club with an implausible lead during an exhibition against English champion Chelsea.

It was a series of remarkable accomplishments for a quiet, undrafted defender called upon by a championship team to replace a departed all-star, Ryan Nelsen.

But then about a month ago, shortly after allowing his third own goal of the year, Boswell's minutes per game plunged from 90 to 0.

The protracted MLS regular season -- three times longer than an NCAA campaign -- was taking its toll.

So Coach Peter Nowak moved newly acquired Facundo Erpen, who had been playing out of position on the right side, into Boswell's central role. The arrangement remained that way -- Erpen orchestrating the defense, Boswell sitting on the bench -- for three league matches and a pair of international games.

"We weren't looking to point fingers, we just wanted to change something because, mentally, when you compare the college season to the professional season, it's a big difference," Nowak said yesterday. "Sometimes you become too tired mentally when you have so many games, and Bobby played in all of them."

On Wednesday, though, with United in a stretch of three games in eight days and the regulars in need of a break, Boswell made a splashy return to the lineup by scoring the opening goal during a 3-1 victory over Real Salt Lake to help United (16-9-5) extend its winning streak to four. Chances are, he will be back in a reserve role tonight when the MetroStars (10-9-11) visit RFK Stadium.

"Through all of this, I have just tried to keep the big picture in mind -- that we're trying to win a championship and I'm part of that puzzle," Boswell said. "The main thing for me is to develop as a player, and hopefully I can do it on the field. If Coach feels differently, I have to respect that and work hard and try to get back out there."

If United's formation called for the standard four defenders, both Boswell and Erpen would probably be on the field at the same time. But United plays with only three backs, and with veterans Brandon Prideaux and Bryan Namoff usually occupying the outside slots, Nowak had to choose between Boswell and the more experienced Erpen in the middle.

Boswell's struggles became apparent in August, around the time of Erpen's long-awaited arrival. The low point came when the former Florida International University standout put the ball into his own net on consecutive weekends, both one-goal losses. It's not uncommon for a defender to suffer the indignity of one own goal during the season, but for it to happen three times was troubling.

"To be involved right from the start of the season was very advantageous for him, but I think he made a few mistakes and I think he understood that," Namoff said. "But he's been resilient in the sense that he was able to bounce back in the last match in Salt Lake. This is a game of opportunities and this was his chance. I thought he played very well and, for his confidence, it was a good boost."

Regardless of how much he plays the rest of the season, Boswell said he has learned from the experience. "I never fatigue, but there was a period where I started to plateau a little bit," he said. "I've learned I've got to be sharp every minute, every game, every play. That's the biggest thing, especially in the back. You can't let down for a minute because you're going to get punished."

United Notes: MetroStars forward Ante Razov (red card) and midfielder Michael Bradley (yellow cards) are suspended. United forward Santino Quaranta is with the U.S. national team in Costa Rica for a World Cup qualifier. . . . United midfielder Christian Gomez was a guest of honor at the White House yesterday as part of Hispanic Heritage Month ceremonies. . . . The team will collect winter clothes for needy children outside Gate A tonight. Donors will receive a ticket voucher and promotional items.

Bobby Boswell, left, is working to get more playing time. "The main thing for me is to develop as a player, and hopefully I can do it on the field," he said.