While playoff action in the NBA's Western Conference seems to be defying logic, that in the Eastern Conference is holding true to form.

"I've been saying all season that Milwaukee is one of the two or three best teams in the league, and maybe the best," said Philadelphia 76er Coach Billy Cunningham. "We're so evenly matched that one mistake by either team can mean a ball game and, maybe, even eventually the series itself."

The best-of-seven Eastern Conference semifinal series between the Buck and 76ers, which is tied, 2-2, resumes tonight at the Spectrum in Philadelphia (WDVM-TV-9 at 11:30 p.m., delayed). The sixth game will be played Friday night at Milwaukee Arena. If a seventh game is necessary, it will be at the Spectrum Sunday.

"We'll just sit and wait and hope they beat other's brains out," said Boston Coach Bill Fitch, whose Celtics beat Chicago in four straight games to advance to the conference finals against the Milwaukee Philadelphia winner.

Most of the attention in this series has been focused on Julius Erving and Marques Johnson. Both are incredible one-on-one players who also have the ability to blend their games into a team concept.

In the first game of the series, Erving scored 38 points and had nine rebounds and six blocked shots.

In the fourth game Sunday in Milwaukee, Johnson came back with 35 points, eight rebounds and seven assists. For the series, Erving is averaging 25.3 points and eight rebounds and Johnson is averaging 28.3 points and nine rebounds.

As great as Erving and Johnson are, the key figures in the series still are centers Darryl Dawkins of Philadelphia and Bob Lanier of Milwaukee.

The Philadelphia press, which is not noted for being patient with stars who don't deliver, jumped all over Dawkins after the first two games of the series and he responded with a strong performance in the third.

Lanier was too much for him in the fourth game, however. Lanier scored 23 points and had nine rebounds. Dawkins had only seven points, five rebounds and fouled out for the second time in the series.

The Bucks, playing in the Eastern Conference this season following a realignment due to the admission of the Dallas franchise, only recently became formidable again, after they acquired the 6-foot-11 Lanier from Detroit last season.

When Lanier joined the Bucks last year, they were 29-27. They went on to win 20 of their last 26 regular-season games. They lost to the defending-champion Seattle SuperSonics in the last minute of the seventh game of the Western Conference semifinal playoff series.

"Bob just seemed to open up everything for us," said guard Quinn Buckner. "He's a great scoring threat around the basket and that creates more opportunities for the rest of us."