The Celtics face the best team in the league tonight (at least as far as standings go). They have an MVP candidate in Paul George and Roy Hibbert is one of the best centers in the league, but the biggest reason they are so good is their defense (which the two players mentioned are a huge part of).
The Fundamentals: How the best defense in the NBA got even better this season | The Point Forward - SI.com
A bit more astonishing, though, is the degree to which Vogel and his team have succeeded in their defensive goals. After allowing an impressive (and league-leading) 96.6 points per 100 possession last year, the remarkably stingy Pacers have held opponents to a jaw-dropping 91.4 points per 100 through 10 games this season. Even if that margin of improvement is halved by season’s end, it would stand as the best single-season improvement by a top-rated defense in NBA.com’s database (which dates to the 2000-01 season). Should they somehow maintain their current, incredible success over the full season, the Pacers’ mark would also be the best team defensive performance in the database’s range, with the 2003-04 Spurs the only team to even come close.
They are scary good on defense. Like 2007-08 Celtics good, if not better because they have younger legs and have played together longer.
They also got a better bench in the offseason and have watched Lance Stevenson blossom into a dynamic weapon for them.
It is a credit to Larry Bird and the rest of the Pacers front office what they've been able to put together there. The Celtics, I'm sure, are taking notes.