Forget that Wes Unseld's knees ache constantly and that he jumps off his right leg because his left leg has no spring. And forget that he is supposed to be quietly playing out the last season of a remarkable NBA career while the Bullets gradually prepared Mitch Kupchak for his spot.

Consider for a few minutes what this almsot-32, 6-foot-7, injury plagued veteran has done over the last month.

He has taken on pro basketball's best pivot men - Kareem Abdul-Jabbar, Bob Lanier, Bill Walton, Artis Gilmore, Dave Cowens, Dan Issel, Marvin Webster - and has more than held his own. In the process, he has given them a lesson in the intricacies of basketba11, especially rebounding.

He has lifted his game over the last 17 contests to the level of three years ago, when he led the league in rebounding. And he has done it against younger, taller, more agile opponents who aren't hampered by knees that make day-to-day living uncomfortable.

In those 17 games, starting with Kupchak's injured thumb. Unseld has averaged 15 rebounds, almost one more than he did in winning the rebounding crown in 1974-75. And that average, projected over the season, would put him second only to Truck Robinson in the NBA this year.

He has also set those monstrous picks that are his trademark. He has raised his scoring average to almost 10 a game and his assist to nearly five. And he has played more minutes than anyone thought his knees could endure.

In four of the last five games, he has been in for at least 40 minutes, including a 41-minute stint against Golden State on Sunday after having his knee drained before tapoff. Although he admits his knees are stiff and that tendinitis prevents him from straightening his right leg completely, he says he can continue to play at this pace the rest of the season.

"I have no doubts about it," he said. "My knees hurt, but they're hurt like this for the last three or four years. Extra playing time won't make much difference with them. I'm not going to die during a game playing like this."

Unseld, the quiet man who prides himself on never complaining about pain, shrugs off what he has accomplished the last month.

He had read about how he was slowing down and how his knees were preventing him from performing as well as he had in the past. He knew thatmany took his statistical decline last season as indication that he was over the hill, ready for basketball medicare.

If given enough minutes and rested at the proper times so his knees don't stiffen, he feels we can still rebound with any center in the league.

"Minutes are important," he said yesterday on the eve of the Bullets' game today at Milwaukee (8:30 p.m., WDCA-TV-20). "But they also have to be the right minutes. For the first time in two years, I'm playing into the second quarter and for me, that's a plus.

"The biggest problem I have is that once my knees stiffen, I have trouble getting them loose again. So the longer I play without coming out, the better. And that is what was happening when Mitch was hurt.

"I've always said that the easiest minutes are in the second and third quarters. You are dealing with guys who are tired. If I can sty in the flow and play, it allows me to wear a guy who are tired. If I can stay in the flow entire game, he isn't going to beat me, because he's going to get tired trying to hold me off."

Unseld has never had any business competing successfully against the Chamberlain, Russell, Abdul-Jabbar or Walton. And that should be even more so now, since he has lost some of his agility and much of his always-limited spring.

But because he never relied on the natural gifts of most great rebounders, he has found his basic strengths have not diminished with age.

"It's now new sthat I've never been tall or that I've never been able to jump very high," he said. "My rebounding has always been based on position, timing, knowing the flow of the ball, reading where it's going, things like that.

"Those are mental things and I've still got them. I still can think out there."

He also still has massive bulk and great strength. "It's like trying to go around a ship," says New Orleans' center Rich Kelley about playing against the 245-pound Unseld.' 'He's always leaning on you."

Unseld goes into every game determined to use his muscles to offset his height. He never lets up; he leans and pushes and works purposely to sap his opponents energy. Down the stretch "I know I'll be stronger. Lots of guys in this league are as strong as I am but not many of them are willing to use it time and time again, every second they're out there."

The league's young centers are no match for a long playing Unseld. In the last month, he has gathered 18 rebounds against Robert Parish, 17 off Swen Nater and 21 off James Edwards. In the same span, he also has managed 24 rebounds; his highest in three years, against Dennis Awtrey and Alvan Admas of Phoenix; 18 against Issel and 12 each against Walton and Abdul-Jabbar.

Now, Bullet Coach Dick Motta is faced with a dilemma. Kupchak is healthy again, eager for playing time. But Unseld has proven that he is more effective with less rest.

Kupchak doesn't get his minutes at center, where do they come from?

"All that is a coaching decision," said Unseld. "I do what they tell me. I'm paid to play, and when I play, I do my best. It's not really very complicated."

Nor is he concerned, he says, about retirement. "What I've done the past month hasn't affected me," he said. "It's still the same. I'll wait until the end of the season and then I'll make a decision.

"I don't have any illusions about what I've done. If I don't produce, if I don't get in the flow of the game, I don't expect to play. If I do something out there, I hope I stay in There's no other way to look at it."