Week 3 of the 2014-15 NBA season is complete, and it's time to update the weekly power rankings.

The defending NBA world champion San Antonio Spurs and high-flying Los Angeles Clippers are struggling early on, but other teams are thriving, making our top five. We've see some big disappointments such as the Los Angeles Lakers and the New York Knicks, and the Miami Heat have been in a slump, dropping out of the top five.

Here are the top five NBA teams after three weeks of play:

1. Memphis Grizzlies

The Memphis Grizzlies aren't the most exciting team, but they get the job done. For the second consecutive season, the Grizzlies have the No. 1 ranked defense in the NBA. Marc Gasol and Zach Randolph have been dominating the boards, and all of a sudden 38-year-old Vince Carter is playing a big role in the offense. The Grizzlies are allowing the fewest points against in the league, just 91.5 points per game. Offense remains somewhat questionable, but for now, the Grizzlies are No. 1.

2. Houston Rockets

Just one game behind the Grizzlies in the Southwest division are the Houston Rockets. The Rockets have made huge improvements on defense from last season, as they rank second in the league. James Harden leads the Rockets in scoring with 23.7 points per game, and Dwight Howard continues to rebound at will. Unfortunately for the Rockets, they got put in their place against the Grizzlies in a 119-93 lopsided defeat. As usual, the Rockets are shooting and making a lot of perimeter shots. Jason Terry and Trevor Ariza lead the Rockets in 3-point shots made so far, and thus opening the door for Harden and Howard.

3. Golden State Warriors

The Golden State Warriors are in first place in the Pacific Division at 8-2. They let a sure victory against the San Antonio Spurs slip away, but with the second-best scoring offense in the league, the Warriors can afford it. Stephen Curry is averaging 24.8 points per game, and he ranks second in three point shots made with 31, just four behind Damian Lillard of the Portland Trail Blazers. Having the 15th ranked defensive squad could halt the Warriors from advancing in the playoffs yet again.

4. Toronto Raptors

The Eastern Conference is in no way shape or form as tough as the Western Conference, but the Toronto Raptors are playing great basketball. At 8-2, the Raptors are the only team that even has a winning record in the Atlantic division. The Raptors haven't defeated many high quality teams, but their only two losses have come against the Chicago Bulls and the Miami Heat. Thanks to Jonas Valanciunas and DeMar DeRozan, the Raptors are one of the most balanced teams in the NBA. The Raptors rank No. 9 in defense and No. 5 in offense. Point guard Kyle Lowry is on pace to have one of the best seasons of his career.

5. Dallas Mavericks

The Dallas Mavericks join the Grizzlies and Rockets as the third Southwest team in our top five. Normally, an 8-3 team wouldn't be in third place, but this division is as tough as it gets. Even the San Antonio Spurs sit in fourth place. The Mavericks have the best offense in the NBA this season, and they've been one of the best perimeter shooting teams in the league. Dirk Nowitzki continues to hit jump shots, and center Tyson Chandler is right back home grabbing rebounds where he won a championship three years ago. The Mavericks have one of the deepest rosters in the league thanks to Donnie Nelson and Mark Cuban.

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