A year ago this week, the Boston Celtics started to become the Boston Celtics of old again. Tortured memories of an 18-game losing streak, Tony Allen’s torn ACL and a 24-58 overall record in 2006-07 were instantly erased. Literally overnight, Danny Ainge went from a trade-happy, mad scientist without a plan to the NBA Executive of the Year. The new Garden inherited a new Big Three. Glory was restored and no one thought twice about Al Jefferson. Led by Paul Pierce, Kevin Garnett and Ray Allen, the Celtics went 66-16 and defeated Kobe Bryant and the Lakers in the 2008 NBA Finals. After 21 fruitless years, banner No. 17 was finally achieved. Somewhere Red Auerbach lit a cigar and smiled. So where do the Green go from here? Can Doc Rivers’ bunch possibly improve upon last season’s staggering .805 win percentage? Will we ever see a better performance than their 131-92 shellacking of Los Angeles in last year’s game six clincher? From here on out, as long as the Big Three are intact, nothing less than a championship will suffice. For the younger generation of Celtics fans, this is the 1980s that we were not old enough to experience. After all, we’re not used to this kind of shamrock dominance. We were victims of a post-Bird era plagued by failure and tragedy. A lot of us are too young to remember the Old Garnen. We were in second grade when Reggie Lewis, the Northeastern star expected to carry the franchise, had a sudden heart attack and died in 1993. In middle school we watched Rick Pitino destroy the franchise by trading away Chauncey Billups and throwing mega-contracts at duds like Travis Knight and “Never Nervous” Pervis Ellison. All we knew of winning was Antoine Walker, Kenny Anderson and a young Pierce in the 2002 Eastern Conference Finals against the Nets. Before Kendrick Perkins we had Vitaly Potapenko. Walter McCarty never played but we loved him anyway. Despite the loss of James Posey, today’s Celtics aren’t just favored to win, they’re expected to. The Big Three are back and have a year of experience under their championship belt. Rajon Rondo is becoming an elite point guard and Perk is looking more like a true center. The supporting cast is deep. Eddie House returns and Tony Allen is almost fully recovered from his horrific showboating injury.