If Tuesday's NBA draft is considered by most personnel officials around the league as the deepest in a long time, then why have the telephone lines been so busy since the Boston Celtics picked up their 16th league championship last Sunday?

Names of such established stars as Robert Parish, Mark Aguirre, Buck Williams and, yes, even Jeff Ruland have been bandied about just as much as the names of such collegiate standouts as Len Bias, Chris Washburn and William Bedford.

The reason? Given the depth of the draft, a team has more chances to fill a specific need with its pick or multiple needs by trading away its choice for proven veteran players.

The Washington Bullets are counting on the depth of the draft to get an immediate impact player. They have the 12th pick, and although General Manager Bob Ferry isn't saying much, the team is believed to be leaning toward Dwayne (Pearl) Washington, the Syracuse point guard, or John Williams, the Louisiana State forward, if either man is still available.

"You're a lot better off if you can make a deal," said Donnie Walsh, general manager of the Indiana Pacers, who will pick fourth on Tuesday. "In the draft, you can fill one weakness. With a trade, you can fill more than one spot. . . . I'm more interested in receiving more than I give up."

That was the thinking behind a potential trade that fell through last week between the Pacers and the Celtics. The champions would have sent center Parish and a player to be named, possibly guard Sam Vincent, for the No. 4 choice. Indiana, which eventually decided against the deal, would have filled two needs: center and point guard. Boston, which already holds the No. 2 choice, would have been in position to secure two of the top four players coming into the league.

The consensus from league talent scouts is that those four are center Brad Daugherty of North Carolina, who is expected to be the first player chosen by Philadelphia; center Bedford of Memphis State; center Washburn of North Carolina State, and forward Bias of Maryland.

Bias is considered the best all-around player in the draft. Boston is strongly interested in him, but picking him could leave the team vulnerable at center in the near future, given the advanced ages of Parish and Bill Walton, who are in their 30s.

The Celtics' problem is the same as those faced by other teams in recent seasons. For example, the Portland Trail Blazers decided to take center Sam Bowie over guard Michael Jordan two years ago. The difference this season is that teams picking at the end of the opening round could have a problem deciding whom to take.

"We've got five guys on our list, ranging in height from 6 feet to over 7, and I don't have any idea who is the one to take," said Milwaukee Coach Don Nelson of his 22nd choice. "They all play different positions and they all have warts of some sort, but they're all quality players."

Nelson's refrain is a familiar one throughout the league.

"There are no dominant players like the Ewings and Olajuwons, but there's no big drop-off either," said Pat Williams, general manager of the Philadelphia 76ers, who have the first and 21st picks on Tuesday. "Two years ago, there were Akeem Olajuwon, Sam Bowie and Michael Jordan, but after No. 8 you were talking about the Michael Cages, Leon Woods and Lancaster Gordons.

"That makes for tougher decisions, because it's possible that the player picked at No. 10 will be as effective as the guy picked No. 2. The guy picked at 5 may be more productive than the No. 1, and the guy selected 15th may actually be a better player than the one picked at No. 5. It's interesting and fun, but there's more pressure, too."

If quality is the major buzzword for this year's draft, safety would have to be a close second. That's why the 76ers most likely will select Daugherty. Although he's not considered as aggressive as Washburn and not as talented as Bias, he's a 7-footer with the right credentials: four years with one of the masters, Dean Smith.

Washburn's past problems -- academically and with the judicial system -- haven't endeared him to some NBA teams, and others were less than impressed when the 6-11 center visited their cities.

Bedford has vast potential, but there has been somewhat of a stigma attached to players from Memphis State. Said one West Coast general manager: "I think he'll be the next LaRue Martin," a center the Trail Blazers selected with the No. 1 pick in the 1973 draft who flopped soon after.

The hesitation to take that risk spurs some teams to pursue trades, just as depth at a particular position tends to initiate conversation. Said Rick Sund, player personnel director of the forward-laden Dallas Mavericks: "As long as there is depth, there will be phone calls."

And more and more phone calls. Nelson says a frequent talker is Ferry, who "called me to see if I was mad at him because I hadn't called looking to talk trade."

Pete Babcock, player personnel director of the Denver Nuggets, says Ferry "is one of the few guys who's not afraid to pull the trigger and make a deal if he thinks it'll help his team."

In the last two drafts, deals made by Ferry have brought the Bullets Gus Williams, Cliff Robinson, Dan Roundfield and Manute Bol. That record, say most of the personnel people, is the exception rather than the rule.

"Ninety-five percent of what people do is just talk because teams don't want to trade as much as they think they do," said Walsh. "They begin to see the down side. They think about the guy they trade away coming back and hurting them, and suddenly he looks better than he did before.

"Every day I come into my office with an idea of what I want to do, then I focus in on what I can do. I'm absolutely willing to deal. My team just has to be better off than it was before."

One way or another, a number of teams will be able to make that statement Wednesday morning.