After 17 years with the Washington Redskins, cornerback Darrell Green acknowledges that "the sun is setting" on what has been a brilliant career at one of football's most taxing positions.

But Green said yesterday that the timing of his retirement won't be tied so much to his physical condition as to his progress toward building a $10 million endowment for the Darrell Green Youth Life Foundation, the cause that has become his life's work.

"You don't have to say it: I'm 39 years old," Green said, asked about his plans for retiring. "The sun is setting. But does it mean I don't enjoy or am not still capable of doing my job? Of course I am."

Green said he feels "pretty good" about his game, despite the Redskins' shift to a zone defense on passing plays that doesn't make the most of his man-to-man cover skills. And as he pursues his charitable work in the Washington area, Green is shrewd enough to see the benefits of playing for the most prominent team in the nation's capital.

But the seven-time Pro Bowl selection also acknowledged the frustration of playing on a defense that is ranked last in the NFL, despite a wealth of talented players.

In an interview with Washington Post editors and reporters, Green attempted to explain the defense's poor results this season, spoke about his reasons for starting his foundation and sketched out his vision for life after football, which will center on his charitable work, church and family.

Green said problems with the defense begin up front, with an inability to stop the run.

"This is not a knock on anybody," Green said. "I think the problem does begin--it may end back there with us [defensive backs]--but it always begins up front. Everybody knows you run the ball on offense, you stop the run on defense. . . .

"When we were losing the last few years, we couldn't run the ball. The offensive line was in shambles, and we were trying to get where we wanted to be, and we weren't able to do it. Now, we can run the ball. We've got the number one back in the league [Stephen Davis]. Not only is he running, but now the pass is open. . . . Whatever our issue is, it begins up front against the run."

Green acknowledged that defensive players have made mental mistakes, as coaches have said. And he agreed, as many have observed, that the Redskins' smaller linebackers have found themselves mismatched this season against heftier opponents. But Green doesn't believe either issue is the heart of the problem.

He characterized second-year linebacker Shawn Barber as being "in the Monte Coleman mold." "Certainly I think those guys are very capable," Green said of the linebackers.

As for players' mental gaffes, Green said they are invariably a part of the game. "We're human beings; we're not robots," he said. "Sometimes you call a play and, boom, you go blank. You go the wrong way, or you make a wrong step. So the coach will say that blanket statement: 'He had a mental lapse.' You could say that every day of the week."

What fans and analysts often overlook in critiquing the defense's performance, he said, is that the opponent may simply be better.

"Sometimes there's a guy named [Doug] Flutie over there; there's a guy named [Troy] Aikman over there," Green said. "And those guys are capable, too. It's not a cop-out. But sometimes you have to just say, 'That guy did a great job.' "

The Buffalo and Dallas quarterbacks handed the Redskins (5-3) their three losses this season. It was in the Oct. 24 loss to Dallas (38-20) and last Sunday's loss to Buffalo (34-17) that Green had his toughest outings, going up against wide receivers Raghib Ismail and Eric Moulds, respectively.

As a defensive player, Green said he measures his own success by the team's success. Through the years, he has had to adapt to the role various defensive coordinators have asked him to play.

"I'm really a man-to-man cover guy. That's what I do," Green said. "Within the context of this defense, it's not the same philosophical thinking that we used to have: 'Put Darrell on Jerry Rice. . . . '

"As my career has gone forth, I've had to adjust to two other defensive coordinators, who, in large part, don't play the same way I played. And so when you talk about how do I feel about myself, I think within the context of what I'm asked to do, I feel pretty good about it."

At 39, five years older than Redskins owner Daniel M. Snyder, Green describes himself as an old-school player and person--the sort who trains hard, does what coaches ask and naturally remembers to say "yes, sir," "yes, ma'am" and "thank you."

He has seen players change around him, just as he has seen society change. And his Darrell Green Youth Life Foundation, founded in 1993, is one man's attempt to offer the best of life's values--opportunity, education, integrity--to children in the Washington area, Green's adopted home.

The foundation's learning center, based in Northeast Washington, currently works with 38 students, ages 5 to 12. Through his fund-raising efforts, Green said he hopes to build three more learning centers (one in each quadrant of the city). He also hopes to help other communities start similar centers around the country and hopes to establish a training center to prepare others to start their own charitable foundations.

The foundation has an annual budget of about $530,000. An endowment in the $10 million range, Green said, would ensure stability.

"I love doing this," Green said of his work with the foundation. "This is what I'm committed to. But there is no this had I not been drafted number one by the Washington Redskins; don't fool yourself."