Could cracks be developing in the Boston Celtics' wall of invincibility?

When the Detroit Pistons beat the defending NBA champions, 125-117, in Game 3 of their Eastern Conference semifinal series, Boston forward Cedric Maxwell shrugged it off. "Even blind dogs get a bone every once in a while," he said.

Following the Pistons' 102-99 victory last Sunday in Game 4, which the Celtics led by 11 points entering the final 12 minutes, Maxwell was gnawing on a different dish.

"Today is one of the times to eat crow," he said. "We had them submerged. They were under water and sinking, but we let them up. Sometimes we turn it on and turn it off and I think it caught up with us in Detroit."

As a result, instead of being able to end the series with a victory at the Boston Garden tonight in Game 5 of the series, the Celtics are struggling to find an edge.

The loss Sunday marked only the fourth time in 62 games that Boston lost after holding a third-quarter lead. "All we had to do was score 18 lousy points in the fourth quarter," forward Kevin McHale said. "If we had done that, just been patient in the offensive end, it wouldn't matter now how unstoppable Vinnie Johnson was."

But because Johnson scored 22 of his career-high 34 points in that final period, as opposed to 12 for Boston, the matchup has become a best two-of-three miniseries, a thought the Celtics found distinctly unappealing.

"Everybody's pretty ticked off about the way it's transpired, letting them back from 2-0," McHale told the Associated Press after yesterday's practice. "They're ready to play some ball."

"The intensity in practice today, the way guys were going at each other, is as much as we've had in any playoff game, if not more," M.L. Carr said. "If we can carry over the toughness we had today . . . there's no doubt what will happen."

The Pistons aren't exactly quaking in their high tops over the pronouncements from Boston, but at the same time they realize they are in a precarious position. "I'm not sure we can keep on rolling sevens," Detroit Coach Chuck Daly said. "We're going to need the kind of individual effort Terry Tyler gave us in Game 3 or that Vinnie gave us Sunday. Somebody's got to do that."

There are likely candidates to be found along the Pistons' front line. Center Bill Laimbeer has been on a roller coaster, scoring one, 12, 27 and five points in the four games.

Forward Kelly Tripucka has been grounded, averaging slightly over 12 points a game in the series, almost 10 under his regular-season norm. But for the series, Detroit's substitutes have outscored Boston's, 155-89.

Despite their back-to-back losses, the Celtics are maintaining that few adjustments are necessary.

"Why should we?" Coach K.C. Jones said. "We were good enough to get an 11-point lead after three quarters."

"We've been through some tough series before but this is going to bring the best out in us," said forward Larry Bird, limited to two points in the fourth quarter of each of the last two games. "I've had my downs and now I'm ready for some ups."