Of late, that has seemed so much ancient history. Going into this season, Boston hadn’t won a title in five years nor reached the championship round in four. Those nerdy black high-top sneakers that are a Celtics trademark seemed appropriate for a bunch of guys who, for the past two seasons, couldn’t get a date to the second round of the playoffs. With the same three aging stars who had anchored the club since 1980 - Larry Bird, 34, Kevin McHale, 33, and Robert Parish, at 37 the oldest player in the NBA - prospects appeared dismal.

What a breathtaking difference half a season makes. As the NBA heads into the stretch run, the Celtics, to the surprise of almost all the experts, are back atop the Eastern Conference - and they seem likely to challenge preseason favorites Detroit, Portland (Ore.), Los Angeles and Chicago for the championship. By last Saturday, Boston had compiled a record of 40 wins against only 13 losses - and opened a cushy double-digit game lead in the divisional standings over Philadelphia. Phoenix Suns president Jerry Colangelo calls the current Celtics “an absolutely amazing job of restructuring.” Even those accustomed to Celtic success are stunned. “Never in my wildest imagination did I think anything like this was possible,” says Boston Globe columnist Bob Ryan, who has chronicled the team for two decades. “I thought we would have to wait for a whole new Celtic generation.”

The 1990-91 Celtics are something of a new generation: three familiar faces and four pairs of swift, young legs. The newcomers include Reggie Lewis, 25, whose Reebok commercial is testament to his imminent stardom; Brian Shaw, 24, who returned from a one-year sabbatical in Italy; Kevin Gamble, 25, a seldom-used scrub turned starter who is second in the league in shooting accuracy, and Dee Brown, 22, a 6-foot-1 rookie who punctuated this new, flashier era by becoming the first Celtic ever to enter the NBA All-Star slam-dunk competition, and then win the contest.

At bottom, though, this version of the Celtics is decidedly traditional. It emphasizes the same team basketball approach Boston has employed since Red Auerbach and Bill Russell launched the dynasty in 1956. No Celtic is among the league’s top 25 scorers, but six Celts average between 14 and 20 points a game. Rookie coach Chris Ford has abandoned the slow grind-and-bang offense of recent vintage and resurrected the running game Boston patented, but later ceded to the rival Los Angeles Lakers.

Boston’s somewhat jaded fans are not given to rendering their judgments at midseason. “Championships are the only measuring stick here,” says coach Ford, who won a ring as a player with Boston in 1981. Veteran Celtics watchers believe this team does have the mettle to still be playing well into baseball season. Ex-Celtic star and coach Tommy Heinsohn, now the team’s TV broadcaster, says Boston boasts the right combination of speed and size - he calls them the “zips” and the “zaps” - to win it all. Meanwhile, up in the rafters, even the ghosts are agog.