Mike Petke is one of the most durable defenders in MLS, even if he isn't the most celebrated. For five years beginning in 1998, he toiled for the MetroStars before D.C. United acquired him in a major trade going into last season. With a Ripkenesque attribute for playing despite injuries, Petke has continued to be a stalwart on the back line for United just as he was in setting a MetroStars record for games and minutes played. There are, naturally, differences between Petke and baseball's "Iron Man," Cal Ripken. Unlike Ripken, Petke has never played on a championship team. But now the possibility looms as never before.

Like his United teammates, Petke seems eager to make the most of Saturday night's Eastern Conference final against New England at RFK, with the winner to play Nov. 14 for the MLS Cup. If anything, his approach to soccer has become even more serious than it was -- more team-oriented, perhaps -- just at the time when D.C. United is playing its best soccer in his two seasons here, and, in fact, its best since its last championship season in 1999. "I don't know of any team in this league that would be in this situation and not up for the game," he said yesterday after United worked out in a cold, hard rain on RFK's auxiliary field.

Petke's performance Saturday could be pivotal because Ryan Nelsen, team captain and middle of the three-man back line, will have to sit out the game because of accumulated yellow cards, as will midfielder Dema Kovalenko. Nelsen has been the centerpiece of a defensive wall that has held opponents scoreless in four of United's last five league games, all victories. "Obviously, when Ryan's in there, he's a leader. That's a huge loss for us," Petke said. "As far as I'm concerned, he's the best defender in this league."

Coach Peter Nowak is mum on how he will arrange his three backs, except to say that Petke will start. Bryan Namoff is expected to take his customary place on the right side. This means that Nowak could put Ezra Hendrickson in the middle and leave Petke on the left, or shift Petke to the middle and insert, perhaps, Brandon Prideaux on the left. In any event, Petke, a 6-foot-2, 199-pounder, will have to play more of a leadership role, if not the game of his life.

Petke is ready, be it in the center or on the left.

"Ezra comes in and he's a big lanky guy and he gets his foot and his head on a lot of things," Petke said. "Traditionally, [the center has] been my favorite position. However, in the last year or two, I've gotten more comfortable on the outside. But I have no problem stepping in there as well. Whoever's in there is going to have a job to do."

"Whoever fills that gap has big shoes to fill," said Namoff, Petke's friend and roommate on the road. "We've talked about it. . . . Staying packed in the back is going to be key. We don't want to get stretched out."

As it would happen, New England's strength is among its forwards. So United's chief challenge likely will fall to its defenders, who will be asked to stop Pat Noonan, adept at both scoring and assisting; an ever-present scoring threat in Taylor Twellman; Steve Ralston, a crisp passer off the wing; and an excellent rookie in Clint Dempsey. "They're dangerous up front," Nowak said.

By his own account, Petke, 28, has matured in different ways on and off the field. Not even a mid-season slump discouraged him for long.

"I'm really at that point in my career when I have nothing to show for it, except for a couple of personal things here and there," he said. "I'd love to get a ring. I don't want to be that guy who goes through, say, 10 to 12 years and never has anything to show for it -- you know, a decent player on bad teams. I'm willing to sacrifice, be whatever type player [Nowak] wants me to be, to be on a good team and win a championship.

"I don't want to say my priorities have gotten in order, because I thought they were always there. But some things that were important to me before are not so much important to me now."

Certainly, his looks have changed. The bleached-blond streaks in his hair from seasons past are gone; he has close-cropped black hair, with sideburns. As a new father, he has found himself waking up at odd hours to new realities; six weeks ago, his wife Kim gave birth to a son, Dylan Michael. "It's been a joy," Petke said, "and it's changed me." He is pleased by the change, too, that brought him to Washington after spending most of his life not too far from Manhattan.

He grew up on Long Island, where his father worked on the railroad for 35 years, almost never missing a day on the job no matter how he might have felt -- Petke's model.

"If you look at the beginning to the middle of this season, we had a lot of guys trying to do too much on their own. We had a lot of guys who weren't willing to do more than what their specific role was," Petke said. But not since the all-star break, he added; since then, everyone has been helping each other.

"Do I think we've reached our peak? I hope not. If not, we're on our way.

"This is, honestly, the first time I've felt confident that we have a good enough team, that if we do what we can do, what we're known to do, we can put ourselves in the championship game."

Mike Petke, left, here battling L.A.'s Ryan Suarez, has helped United keep opponents scoreless in 4 of past 5 games.