Don Nelson spent his playing career with the Boston Celtics and spent the past week trying to beat them. He had a far better time playing than coaching.

"I'm not sure that Boston isn't on a different planet than the rest of us mere mortal teams," said Nelson, who admitted that, after his own Milwaukee Bucks, he roots for the Celtics.

And now he will have a chance to do just that as the Celtics advance to their 18th NBA championship series (in which they are 15-2), and face either the Houston Rockets or the Los Angeles Lakers. The Lakers defeated the Celtics in last year's finals but are trailing the Rockets, 3-1. Only four teams, including the 1970 Lakers, have come back from 3-1 deficits to win seven-game series.

Nelson's Bucks returned to earth with a thud Sunday afternoon when the Celtics completed the sweep of the Eastern Conference final series by winning Game 4, 111-98.

Nelson played on four NBA championship teams in Boston, so he understands the Celtics tradition and its legacy of great players. There is no question that Larry Bird fits that category.

The all-star forward recognized that his team was sputtering a bit in the third quarter Sunday, so he took charge in the fourth. Bird scored 17 of his game-high 30 points in the final period and 12 of them came on three-point shots.

Asked what level he thought Bird's play to be at, Nelson said, "Bird's level."

Not every player has a level named after him, but then few can do what Bird does.

"I hope all the other Celtics realize what a privilege it is to play with Larry Bird," Nelson said. "I remember that it was a privilege to play with people like Bill Russell and John Havlicek and Dave Cowens."

The Bucks were outscored, 32-16, in the fourth quarter, which began with Milwaukee ahead, 82-79.

"Today we had more confidence that we could come back," Bird said. "We did it Saturday . If the game's close in the fourth quarter, there's no question we're going to win."

Bird's pass to Robert Parish for a dunk gave Boston the lead for keeps, 85-84, with 10:55 to go in the game.

It was still a game when Milwaukee's Sidney Moncrief, who played valiantly on a sore left heel, made a free throw to cut Boston's lead to 95-92 with 5:21 left.

But then came the Bird barrage. In the span from 4:06 to 1:40, Bird hit two three-pointers in a row, then two free throws and another three-pointer, which pulled the Celtics away, 106-94. Bird -- who was fourth in the league in three-point shooting (82 of 194, .423) during the regular season -- finished the day five for six from the outer reaches.

"Larry has no conscience out there," said Danny Ainge, who was three for five himself in three-point shooting and scored 25 points. "He's our leader and he does it in every way."

"Today it was unconscious," Bird said. "Especially the three-pointer off the pass from Bill Walton . I was leaning left, just let it go and it went in."

Kevin McHale, who contributed 20 points and a team-high 11 rebounds, laughed when he was asked if he wouldn't mind having his son grow up to be a player like Larry Bird.

"I wish my kid had that talent," McHale said. "I could just carry my golf bag in the summer and watch in the winter."

Milwaukee police said today that tests on an ampule found near the Celtics' bench Saturday produced no evidence that it was anything out of the ordinary. Suspicions were raised by a doctor who found it and a local attorney who made it an issue.

Dr. Robert Wetzler said he saw Celtics players break open the ampule and then inhale. Wetzler thought the ampule resembled one that would be used to contain amyl nitrate, a stimulant that can be obtained only by prescription.

Wetzler gave the ampule to Alan Eisenberg, a well-known Milwaukee attorney who was sitting next to him. Eisenberg took the ampule to Milwaukee police, who questioned Celtics trainer Ray Melchiorre. Melchiorre, who called the incident "ridiculous," gave police another of the ampules, which he said contained ammonia.

"The ampule was examined by our state crime lab, and the examiner is 99.9 percent sure that it is ammonia inhalant," said Capt. Thomas Perlewitz of the Milwaukee vice squad. "It was consistent with the one the club gave us. It was much ado about nothing."