Healthy again, KG in vintage form for hot C’s

Thursday night’s nail-biter between the Celtics and Sixers confirmed it: Kevin Garnett is back, and he has the Celtics atop the Eastern Conference at 18-4 and doing their usual pre-Christmas destruction of the league.

The headliner of the night was the Rajon Rondo-to-KG lob that won the game for Boston. The fact that Doc Rivers called that play instead of an isolation for Paul Pierce or (Rivers’ favorite) Ray Allen-Pierce crunch-time pick-and-pop tells you all you need to know about Garnett’s right leg. As Chris Forsberg notes in his breakdown at ESPNBoston.com, the Rondo-to-KG lob became the sad representation of Garnett’s decline toward retirement last season — a decline few outside the Celtics’ organization thought would reverse itself this season.

But the unexpected has happened. Rondo is lobbing the ball to Garnett at every chance  —  in transition, when KG is the first big guy down the floor; in the half court; and now, remarkably, on a buzzer-beater using a play the Celtics apparently screwed up in practice over and over, according to Forsberg. Garnett is shooting 54 percent from the floor, grabbing defensive rebounds at a career-best rate (think about that for a second), dishing his usual slick interior passes and feasting on open looks all over the floor.

But Thursday’s buzzer-beater overshadowed something that is even more important for Boston’s championship chances: Garnett’s shut-down defense on Andre Iguodala on two last-minute possessions. With 42 seconds left, the Sixers ran a pick-and-roll with Iguodala as the ball-handler, and Boston switched so that Garnett took Iguodala and Pierce took the screen-setter (Elton Brand). It struck me how willingly the Celtics made that switch. Remember how easily Andray Blatche and Rashard Lewis blew by Garnett in isolations last season?

But Iguodala couldn’t do that. Garnett kept Iguodala in front him and stayed right in his face, forcing him to take a ridiculously tough leaner from just inside the foul line. The shot went in, giving Philadelphia a 99-98 lead, but even the guys at Liberty Ballers concede it was a brutally difficult shot that had no business going in.

After a clutch Glen Davis jumper gave Boston the lead with 27 seconds left, the Sixers went to the same play, and again, the Celtics switched Garnett onto Iguodala. And again, Iguodala couldn’t shake KG, and was forced to put up a contested mid-range jumper. This one missed.

Garnett just did not have this in him last year. Iguodala is a quick perimeter player — not some lumbering big guy like Blatche. Iguodala burned Pierce with a crossover a few seconds later to give Philadelphia the lead again.

The Celtics are allowing just 100 points per 100 possessions this season, the best mark in the league and nearly on par with the mark they put up in 2007-08, when they had one of the best defenses in modern league history.

And here’s a pretty interesting thing: Every five-man lineup that includes Garnett and has logged at least 15 minutes has outperformed Boston’s overall defense, according to Basketball Value. That’s seven lineups including guys as diverse as Shaquille O’Neal, Nate Robinson, Marquis Daniels and Davis, and all of them are allowing fewer points per possession than the best defense in the league.

That’s not all because of Garnett, of course. Boston runs a great defensive system, which the core guys have been operating for more than three full seasons now. All of Boston’s key players have proved to be effective defenders within that system. But a healthy Garnett is the player who transforms Boston from a decent defense into a championship defense; check out the numbers from the 2008-09 playoffs, when Garnett was injured, to see how Boston’s D performed without him.

The Celtics, meanwhile, look so good right now that you’re tempted to wonder whether they will maintain this level of play and go for the top seed in the Eastern Conference. They suddenly have a three-game advantage on Orlando in the loss column and a four-game edge on the Heat, and the team has talked the talk about not wanting to play a Game 7 on the road again. Rondo played 47:14 on Thursday despite suffering from a variety of leg and foot problems, and that’s either a reckless decision by Rivers (even given Delonte West’s injury) or an indication that Boston is going hard to win games in December. Or both.

This team has tanked in each of the last two Januarys (and the tanking extended until the playoffs last season), so let’s not get ahead of ourselves. But with one-fourth of the season gone, Boston is the team to beat, and KG’s health is a major reason why.