The National Basketball Association playoffs begin tonight, starting a two-month ordeal to determine the league's champion. Staff writer Paul Attner examines the matchups in both the Eastern and Western conferences and predicts the probable winners.

Center Wes Unseld hopes the Washington Bullets resemble a faucet. Otherwise, he thinks they may have more problems than anticipated while pursuing their second straight National Basketball Association title.

"We have a tendency to turn it on or turn it off, like a faucet," said the Bullet captain. "But that worries me. We are human being, not machines. I just hope we can get back into the groove as quickly as we think we can."

Washington ended the season with three straight losses, its longest losing streak since the opening month of the schedule. But the streak also came after the Bullets had wrapped up the league's best record, giving them the home-court advantage in every round of the playoffs, a luxury they did not have last year.

The combination of a home-court edge, a talented front line and the best depth in the NBA puts the Bullets in a commanding position to reach the final round.

But don't expect a breeze. Even Coach Dick Motta sees a seven-game series in the conference semifinal series-and he won't even talk about the conference finals.

The opponent the Bullets fear most is Philadelphia, despite the absence of injured guard Doug Collins. As long as Julius Erving and Darryl Dawkins remain healthy, the Sixers have a special mystique that evokes respect, no matter how many injuries the 76ers must overcome.

Philadephia hardly is a sure bet to match up against Washington in the conference finals. First, the 76ers must subdue New Jersey (they should do so with ease), then they have to match firepower with unpredictable San Antonio.

The Spurs play like the Harlem Globetrotters one night and the New Orleans Jazz the next. They struggled the last several weeks of the season losing at home consistently, while forward Larry Kenon brooded about his contract situation (he is a free agent) and George Gervin wondered why he also wasn't getting more money. Gervin signed a contract at mid-season .

San Antonio's wonderful guard duo of Gervin and James Silas should overwhelm Philadelphia's small guards. But unless the Spurs remember that rebounding is part of the game, the 76ers can neutralize the guard disadvantage on the boards.

Motta is convinced that no team can be successful in the playoffs trying to win from the outside, which means the Spurs need quick improvement from such members of their supporting cast as Billy Paultz, Mark Olberding and Mike Green to hold off Philadelphia.

Despite a number of close games with Atlanta the last two seasons, the Bullets would have an easier time defeating the Hawks than the Rockets in the other semifinal.

Houston has so many explosive outside shooters-and Moses Malone is so dependable in the middle-that no foe is safe against the Rockets in a seven-game series. Washington learned that lesson two years ago when the Rockets surprised the Bullets in the playoffs with an uncanny display of perimeter marksmanship.

Atlanta resembles a bunch of pesky gnats. No matter what the score is, the Hawks never stop swarming and scratching. That approach irritates opponents but it also wins games for a team with not as much talent as most other playoff clubs.

Still, Houston's home-court advantage should be enough to swat the Hawks and set up a fine series with Washington. If the Bullets survive, they should be primed to handle either San Antonio or Philadelphia in the conference championship.

Atlanta (46-36) Versus Houston (47-35)

If nothing else, this series eventually might be remembered for the vocal gymnastics of the coaches. Atlanta's Hubie Brown is the loudest, most abrasive yeller in the league (usually at his players). But Houston's Tom Nissalke and his assistant, Del Harris, could provide the best one-two punch.

Brown probably will spend most of his time screaming about Houston's shooting. The Hawks play a lovely (and illegal) zone, which works against most teams but should be destroyed by the Rockets' perimeter gunners, especially Calvin Murphy and Rudy Tomjanovich.

"Let them play a zone against us," said Houston forward Rick Barry. "I think we have the manpower to handle it quite nicely."

Barry, the only front-court player in the league who spends most games at the top of the key running the offense, forgets that Atlanta won three of four from his team this year. Over a longer series, the Hawks would be a good bet to win, but not in the almost-sudden-death atmosphere of the miniseries.

Malone, of course, is always available as a safety valve for the Rockets. No single Hawk can handle him man for man, so they will have to sag around the young phenom and hope Houston can hit one of those cold streaks which characterized the Rockets' midseason play.

It would be dangerous, however to underestimate Atlanta. Brown prods and pushes his team like a fanatic, but the Hawks improved by five wins this season. They also have grown stronger since the midseason addition of guard Terry Furlow, who finally gives them an outside threat.

To have a chance, Brown will need solid performances from his five-deep bench and from his forwards, John Drew, who must score heavily, and Dan Roundfield, who must make sure Malone gets little help on the boards.

Philadelphia (47-35) Versus New Jersey (37-45)

The fallacy of the NBA's playoff structure is epitomized by New Jersey's presence in this series. The Nets didn't come close to being a .500 team, yet the Eastern Conference was so bad they coasted into postseason play.

New Jersey's Kevin Loughery is a good enough coach to give the 76ers concern. "He'll come up with something to make it interesting," said Motta. But realistically, a club with only two consistent scorers (Bernard King and John Williamson), a sometimes-horrible defense and inadequate rebounding shouldn't be able to handle Philadelphia.

The 76ers closed with a rush to squeeze out the third-best record in the conference. They won 11 of their last 14 and kept improving even after Collins suffered a stress fracture in his foot.

His absence leaves the 76ers with too many small guards, a weakness that can be exploited during a long series. But don't feel sorry yet for Philadelphia. Just remember last year when the Bullets limped into the playoffs without Phil Chenier and still came out smiling. CAPTION: Picture 1 through 4, playoff luminaries: Kareem Abdul-Jabbar, Left: John Drew, top: Julius Erving, bottom: Maurice Lucas, right. Photos by Richard Darcy-The Washington Post-AP