The two surprise teams of the National Basketball Association, each streaking in unexpected directions, will be on display tonight at Capital Centre (WTOP-1500, 8:05) when the Washington Bullets play the New York Knicks.

The Bullets, a consensus pre-season choice to finish last in the Atlantic Division this season, have a seven-game winning streak and are solidly entrenched in third place with a 22-19 record.

The Knicks, winners of 50 games last season and expected to improve after acquiring Maurice Lucas, have lost eight of their last 10 and have plunged into last place with a 19-23 mark.

How can one team with apparently inferior personnel be so successful while another, loaded with all-stars, founders so pathetically?

Intangibles such as desire, togetherness and hustle usually are not sufficient answers for basketball buffs, although those are the words Coach Gene Shue often uses to explain the achievements of the Bullets.

Indifference, selfishness and disorganization have been some of the accusations made about the Knicks for their inconsistent play. There have been few denials.

Curiously, the Knicks, the veteran team, have been shuffling their lineup throughout the first half of the season. The young Bullets, fortified by free agents, have used essentially the same lineup for the last month.

Despite their 50-32 record last season, Coach Red Holzman was not satisified with the undisciplined play of his guards and asked management to acquire free agents Randy Smith and Mike Newlin. Then he unloaded Ray Williams, a 20-point-a-game scorer, in exchange for Lucas, a rebounding forward who would fill the team's greatest need.

And so the makeup of a title contender was complete. It started with the drafting of guard Michael Ray Richardson, now a three-time all-star. It continued the following year when the seven-footer everyone coveted, Bill Cartwright, was drafted.

Now the Knicks have two seven-foot centers, Cartwright for offense and Marvin Webster for defense. They have an all-star guard, plus two veterans that Holzman wanted for back court stability. They have Lucas, a top power forward, plus a shooting forward in Campy Russell, another rebounder in Sly Williams and even a defensive specialist in the recently activated Toby Knight.

"We just haven't been consistent," said Holzman. "We've had a lot of injuries and haven't been able to settle on a set lineup."

Meanwhile, Shue took John Lucas, who wasn't signed until October, and made him his floor leader. He brought in Spencer Haywood from Italy and installed him as power forward. He told Rick Mahorn, a seldom-used rookie center last season, that he was in charge of the defense. He blended these three and rookie guard Frank Johnson with holdovers Greg Ballard and Kevin Grevey, and developed one of the best defensive units in the league.

In their last six games, the Bullets have allowed only 550 points, an average of 91.6 per game. They held Atlanta to its season's low of 78 and Chicago to its low of 84 on Tuesday.

"The Bullets are playing, without a doubt, the best defense in the league," Shue said. "We've worked hard on it all season and now it's all coming together."

If there is a defensive catalyst to a a team that has held 22 of its 41 opponents to fewer than 100 points, it is Mahorn, the muscular 6-foot-9, 235-pounder from Hampton Institute.

"I try to talk as much as I can, call out picks and let the guards know what's going on behind them," said Mahorn, who is fourth in the league in blocked shots. "We do a lot of helping out: that's one reason why we're able to block shots. A lot of times, it's not my man's shot I'm blocking."

There is a genuine togetherness on this team that extends from the court to a local restaurant near Capital Centre. The players behave more like collegians than jaded or indifferent professionals.

"This is the most enjoyable team I've ever been on," said Lucas, a seven-year veteran who previously played at Houston and Golden State. "These guys are having fun. They really enjoy each other's company."

Grevey has been with the Bullets for seven years. He's experienced the high of winning a world championship and the lows of missing the playoffs. He remembers a nine-game winning streak in 1978, but says this one is better.

"We were coming off a world championship when we had that other long streak," he said yesterday during practice at Bowie State. "We really didn't appreciate it. It was more or less expected. In this one, every game has been meaningful. This team is trying so hard to gain some identity, to accomplish something that nobody expected.

"I'll be honest, I didn't expect us to accomplish what we've done so far. We're not spectacular, but we're playing together, working hard and not worrying about who the heroes are."

The Bullets are not spectacular, and the fans still haven't turned out, much to the dismay of General Manager Bob Ferry. But at the midpoint of the season, there no longer is doubt that this "bunch of no-names," as Lucas calls them, has genuine playoff potential.