Red Auerbach was puffing on his cigar a month or so ago, pondering the good fortunes of his ballclub.

"But you never know what can happen," he said. "One injury and boom - the whole picture changes."Thus, you may have to adjust your set for the next week or so while Larry Bird recuperates at home, trying to persuade an increasingly cranky back to stay out of it and allow him to resume his profession.

The injury serves as a vivid reminder of just how fragile the 1990-91 version of the Boston Celtics truly is.

If there was one concern about the long-term chances of this club, it was the depth. Before Bird went down, the Celtics were ostensibly going with a seven-man rotation, with occasional input from Joe Kleine or Ed Pinckney. Both have acquitted themselves well in the past few days, which is an encouraging sign.

It's not encouraging, however, to watch Kevin McHale go the entire 48 minutes against Milwaukee. Chris Ford was right; he couldn't afford to take him out, yet he can't afford to ask him to pitch a complete game every night until Bird gets back.

"We can stem the tide," McHale said. "But without Larry Bird, we are not a great basketball team. We're only a good one."

The last Celtics team to win a championship (1986) wasn't particularly deep, either, but the makeup was almost exclusively veterans. The Big Three were four years younger. Danny Ainge and Dennis Johnson were manning the backcourt, with Jerry Sichting as the able backup. Bill Walton and Scott Wedman were coming off the bench. Of that group (we are discounting rookie Sam Vincent, who was used sparingly), the youngest was Ainge, at 27.

Now consider this year's entry. Robert Parish is 37, the oldest player in the league. Bird is 34, McHale 33. As for the next tier of key contributors, Kevin Gamble logs in at 25, Reggie Lewis at 25, Brian Shaw at 24 and rookie Dee Brown at 22.

It is an odd mix of the old and the young, including a backcourt whose senior member, Lewis, is playing in only his fourth season. The fact they have done so well to date is a testimony to the players and coaches. At times, however, they show their inexperience, particularly against teams with good pressure defense in the backcourt, such as Milwaukee.

If the Celtics are smart, they will hold out Bird until next week against Detroit, even if he's ready before then.

Does a healthy Bird guarantee another championship? Of course not. An unhealthy Bird, however, guarantees Boston won't win one.