Sunday, with both Kevin Garnett and Kendrick Perkins on the sidelines nursing injuries, the Boston Celtics defeated the San Antonio Spurs at the Boston Garden. It was their first home win against the perennial NBA power since 1997.How did this ever happen? How did the Boston Celtics go from being a team that couldn’t win a YMCA pickup game a year ago to being able to beat Tim Duncan and the San Antonio Spurs without their two primary big men?The answer is easier than you’d think: Garnett.Wait, you say. Kevin Garnett wasn’t even playing. It doesn’t matter. Kevin Garnett is the most important thing that’s happened to the Boston Celtics since Larry Bird came into the league in 1979.There are some players – and it doesn’t happen all that often – who transcend their official roles, and Garnett is one of them. He’s not just a power forward/center. And even though he went to great pains, when he was traded here, to say this was Paul Pierce’s team, even Pierce has to realize that’s not true.This is totally Kevin Garnett’s team.Garnett came to Boston with the reputation as a tireless worker who understood, and accepted, that nobody is too important to do the little things that make the difference between winning and losing. Garnett does them. And if he can do them, so can everyone else.Garnett has completely changed the culture of this team, the same way Bird did in 1979. And in so doing, he makes all the people who swore the Celtics had to lose every game last year so they could get the No. 1 pick in the NBA draft look absolutely ridiculous.Boston’s sports teams have been fortunate through the years to have a few pivotal players, managers and coaches who have singularly transformed their franchises. Bill Parcells immediately comes to mind, because if you’re looking for that transitional figure that jolted the Patriots out of their habitual losing ways, he was it.But if you’re looking for someone who turned his franchise 180 degrees in a different direction, you’d be talking about Dick Williams of the Boston Red Sox, who took over a team that had lost 100 games only two seasons earlier and managed it to an American League pennant in 1967.His imprint was so dominating that even after he left, the Red Sox had winning seasons all the way up through 1983 – the year Carl Yastrzemski retired.What did Parcells and Williams have in common with Garnett? All three accept nothing less than total dedication.One can almost see Garnett in practice, holding all those players to his standards. One can almost see him take Pierce aside and tell him, politely, or maybe not so politely, to keep his temper in check ? that a focused Paul Pierce is one of the best players in the league; but an unfocused Paul Pierce is useless.When Garnett came to Boston, he was billed as a great player, but a greater clubhouse presence. So far, that’s been right on the money. He’s so important to the Celtics that even though he’s injured at the moment, he’s obviously taught this team well enough that it can go out and execute, and play as a unit, without him.There’s a lot of talk that as good as these Celtics are, they won’t be any match for the Pistons if the two teams face each other in the playoffs. Don’t be so sure. If they lose, they’ll go down hard. And it’s just possible that in these last few weeks, without Garnett, the Celtics have taken their cue from him and taken a vital step toward being able to play with the spotlight on them.I like this team. And it’s been a long, long time since I’ve been able to say that.Steve Krause is sports editor of The Item.