When the National Basketball Association playoffs began last week, the Washington Bullets had the poorest home attendance of the 10 teams involved in the first-round series. Only 9,326 of the 19,035 seats at Capital Centre were filled for the opening game against the Atlanta Hawks, the smallest playoff gathering at the Landover arena since it opened during the 1973-74 season.

This is the latest example of what appears to be a two-year trend locally: playoff apathy. "I'm disappointed that we didn't have a better crowd, and I really can't understand why we did'nt" said the Bullet's president, Abe Pollin.

In an effort to unravel the riddle before the Bullets return to the scene of the mass sit-out tomorrow night for game three of the Eastern Conference semifinal against San Antonio, I interviewed some empty seats.

"Why have you been sans posteriors?" I asked, getting right to the bottom of the phenomenon.

"Contrary to appearances, those weren't ordinary backsides you used to see sitting in us for every playoff game," said one seat, who asked not to be identified by number. I will call him Deep Upholstery.

"They were sophisticated basketball fans, and they have gotten a bit jaded. The ghost of playoff collapses past chased them away. They left and said, 'We'll see you again when the Bullets' performance merits our attendance."

"How did this come about?" I pressed him. "What was the sequence of events?"

"Back in 1975, when the Bullets beat Buffalo and Boston to get to the NBA championship series, they were the town darlings," Deep Upholstery whispered throatily. "Practically every game was sold out. People paid scalpers $50 a ticket. There weren't enough of us empty seats to accommodate all the fans' fannies.

"Then, when the team lost the finals to Golden State in four straight games, the bloom was off the rose. It was a huge letdown. The fans figuratively speaking, started to bite the Bullets.

"And when the team lost to Cleveland in the Eastern Conference semifinals the next year, disenchantment really set in. It hasn't been the same around here since. People started saying, "They'll have to do better than this before I pay playoff prices to sit here.'"

I asked him to continue, but he said he couldn't talk in the arena. He suggested we meet out in the parking lot. When we did, Deep Upholstery lit up a cigarette and went on:

There just hasn't been much interest in those first-round 'mini-series' the past two years. We had only 11,240 and 10,488 seats filled for only first-round games against Cleveland last year, and then the all-time low last week for Atlanta - more of us empty seats than full ones.

" Atlanta's not a very strong draw, you know. John Drew, little Charlie Criss, and mostly no-names after that.They never had much chance. People don't want to pay $10.50 for mismatches when there should be better games later on.

"There may not be very many of us empty seats around Friday night and Sunday afternoon, since the Bullets looked so good on TV winning at San Antonio Tuesday night. But they'll have to keep playing that way to make sure the behinds keep coming back.

"Remember, last year in the Eastern semifinals against Houston, we had no empty seats for game four and 6.742 of them for game six, when the Bullets were eliminated at home. They had lost three of four after winning the opener, and the natives were getting restless. [They were unhappy, and found other things to do on a nice springtime Sunday afternoon.]

"Then you're into a vicious cycle. Big crowds help the home team. When the team loses and people stay away, the team plays worse, and then more people stay away, and so on, ad infintum. Ghastly for us seats that don't want empty lives."

Careful examination of statistics and discussions with Bullet front office personnel bore out what Deep Upholstery had said.

Playoff attendance here has been going down since the Bullets were beaten by the Cavaliers in 1976. Up to that point, there had never been a crowd smaller than 16,522 at Capital Centre, and 10 of 15 playoff games there had been sellouts. In six games since, there has been just one sellout and an average of only 11,588 spectators.

Especially during first-round games the arena becomes, as a disillusioned campus activist once called his university, "a hotbed of apathy." The overextended NBA playoff system has put into the opening "mini-series," at playoff prices, teams many fans do not judge worthy of postseason attention.

Even many of the nearly 5,000 season-ticket holders balked at paying $10.50. $8.50 or $6 to see the Bullets shoot down the low-flying Hawks.

"Less than 10,000 at last week's game looks really bad, but if you take out the three 'miniseries' games the past two years, our average goes way up," argued Chip Reed, the Bullets' embattled marketing director.

Granted, but the fact remains that around the league, six of the 12 first-round games were sellouts, and only in Philadelphia (13,011 at the 18,276 seat Spectrum) and Washington were there more than 2,500 empty seats for any game.

"A number of those teams were in the playoffs for the first time, or at least the first time in several years," countered Reed. "Philadelphia is more comparable to Washington. They're used to seeing good teams. They expect more.

"Also, we do something most teams don't: we raise our regular-season price ($9, $7 and $4) the same amount for all playoff games, from the first round all the way through the championship round. A lot of other teams go up a dollar a round. We come out with a lower average playoff ticket price, but it's 'front-heavy' - steep for the early rounds, like Atlanta. Some people questioned that.

"I think our fans were waiting for the second round, sitting back and thinking, 'Hey, if I'm going to pay top dollar to see the Bullets in the Playoffs, I'm going to wait for San Antonio of Philadelphia.' They didn't rally consider the Atlanta game the playoffs.