The Washington Bullets came up with another defensive gem last night, making the New York Knicks their fourth straight preseason victim, 87-74. The Bullets have held all five opponents below 100 points.

The Bullets' offensive excitement was provided by guard Billy Ray Bates, who treated a Capital Centre crowd of 12,751 to some spectacular moves, including one breakaway dunk that had even his teammates applauding in appreciation.

Bates made seven of 12 shots and finished with 15 points and three assists. Spencer Haywood had 13 points and Don Collins and Rick Mahorn 11 each.

Bill Cartwright led the Knicks with 12 points.

In the first game of the doubleheader, guard Eric Floyd, the former all-America from Georgetown, scored 16 points and the New Jersey Nets defeated the Atlanta Hawks, 91-85.

The Bullets will face the Nets tonight in Norfolk in their last exhibition game. Their regular season begins next Friday at Indiana.

"Obviously, you have to say defense was the whole game," said Washington Coach Gene Shue. "It's our defense that has to hold us in every game. This is how we have to play because we aren't going to score a lot of points."

The Bullets outscored the Knicks, 14-2, at the end of the first quarter and the beginning of the second and went on to a 46-36 halftime lead.

Greg Ballard made two free throws, Frank Johnson one and Bryan Warrick and Haywood each had a field goal while the Knicks were turning the ball over four straight times at the end of the first quarter. The Bullets led, 20-16, at the end of the period.

The Bullets began the second quarter by scoring seven of the first nine points, with five coming from Bates to give them a 27-18 lead. The Knicks weren't much of a threat the rest of the game.

Washington blew open the game in the third period by holding New York to 13 points while Mahorn, Bates and Haywood combined for all 23 the Bullets scored. Mahorn had nine, Bates eight and Haywood six.

The Bullets led, 60-47, late in the third quarter when Bates broke away for his rock-the-cradle dunk. Haywood then scored on a driving dunk, and after a turnover by the Knicks, Mahorn converted a three-point play and the Bullets led, 67-47.

Shue was particularly pleased with the play of Bates, the free agent the Bullets signed the day before camp opened.

"He's trying very hard on defense," said Shue, "and he isn't making many mistakes. He's an electrifying offensive player and I think people like to see him with the ball."

The Knicks were woefully undermanned. Earlier in the day, they traded all-star guard Michael Ray Richardson to the Golden State Warriors for forward Bernard King, and also acquired forward Louis Orr from Indiana for a second-round draft choice and cash. Neither was with the Knicks last night.

King and Orr were free agents who had signed offer sheets with the Knicks before the trades were worked out.

The Bullets started the same lineup of Mahorn, Ballard, Haywood, Warrick and Johnson that had begun the previous four games. Barring unforeseen happenings, that is the lineup with which the Bullets will open the season.

The only Bullets who didn't play were guard Kevin Grevey and forward Charles Davis. Grevey hasn't practiced yet this season because of a torn abdominal muscle; Davis has strained ligaments in his right knee. He won't play tonight, but will practice Monday. Grevey will be out indefinitely and will probably start the regular season on the injured list.

Floyd, New Jersey's first-round draft pick, started for the first time in the preseason. He scored nine of his points and had three rebounds in the third period when the Nets broke open the game.

Former Maryland center Len Elmore and Floyd teamed for 10 points late in the quarter as the Nets outscored the Hawks, 10-2.

Forward Albert King, another former Terrapin, had 10 points.