NBA MVP Power Rankings are back, and there's a new man on top of the leaderboard. That man would be James Harden, who leads the league in scoring and does a bit of everything for the Houston Rockets. The previous holder of the top slot, Stephen Curry, doesn't fall far, but some minor slippage on Curry's part was just enough for Harden to pounce.

1. James Harden (Previous ranking: 2)

Harden's December has been phenomenal. The Rockets guard is averaging 30 points, seven assists and six rebounds this month, and his efficiency has jumped after a poor shooting start to the season. He's shooting nearly 47 percent overall and better than 34 percent from three and he's still getting to the free throw line almost 10 times per game.

Harden's best performance of the season came in a 110-95 beating of the Trail Blazers. In just 32 minutes of action, he put up 44 points, seven assists and five steals. The historic performance was his third game with at least 40 points in the span of 12 days.

2. Stephen Curry (Previous ranking: 1)

Curry hasn't been bad over the last two weeks, but there were a few clunkers and only one standout performance. The Warriors have gone 3-3 over their last six games since starting 21-2, and the electric point guard put up duds in two of those defeats.

In a high-profile matchup against the Grizzlies, Curry was held to just 9-of-25 shooting overall and a dreadful 1-of-10 from three-point range. Last week, turnovers were an issue in consecutive losses to the Lakers and Clippers.

As great a season as Curry is having, his three-point shooting has been inconsistent, at least relative to his standards. He's at 38.5 percent from deep on the year, which is good, but also well below his career-worst mark of 42.4 percent last season.

The Pelicans continue to hover around .500, but Davis keeps trucking along with a PER over 32. Davis has retaken the PER lead from Russell Westbrook and the numbers the big man is putting up are some that have only been matched by a few others in NBA history. If Davis were to keep his current numbers, he'd join Shaquille O'Neal and Kareem Abdul-Jabbar as the only players to average 24 points, 10 rebounds and three blocks while shooting more than 56 percent from the field, per Basketball-Reference.com.

And remember, this kid is just 21 years old. The sky is the limit.

Lowry initially struggled with his shooting when DeMar DeRozan went down, but that has changed over the past two weeks. In the last seven games, Lowry has shot at least 50 percent in six of them. His averages over that span are 23 points, eight rebounds and five assists while shooting nearly 53-percent overall and 50 percent from three.

Not coincidentally, the Raptors have won six of those seven games, including both of a tough back-to-back against the Clippers and Nuggets. Toronto now has the best offensive rating in the NBA and the only loss during the seven-game stretch came against the Bulls, who are the hottest team in the league. Speaking of the Bulls ...

It's hard to come up with enough superlatives to describe Butler this season. The improvement he has made offensively is nearly unprecedented, as he has gone from a defensive role player to a borderline superstar over the course of one summer.

Butler won Eastern Conference Player of the Month in November, and he has been just as good, if not better, in December. He's averaging 23 points, seven rebounds and three assists while shooting 48-percent overall and 38 percent from three in December, and he's doing it while playing a huge minutes load. Also:

Oh, Jimmy Butler is also on pace to become the 1st player in NBA history to avg more than 40 minutes per game, yet fewer than 1.5 turnovers. — Tommy Beer (@TommyBeer) December 30, 2014

Butler's elite defense has slipped somewhat because of how much effort he has had to exert on offense, but he still often finds a way to make a big defensive play when needed. This isn't just a fluke anymore. This is legitimate improvement, and you can make a case that Butler is the second-best shooting guard in the league.

It kills me to drop Gasol three spots, because the Grizzlies' recent struggles aren't all his fault. Memphis has gone 1-4 in the last five games, but Gasol averaged 22 points, 10 rebounds and four assists in those contests. Those are better averages than his season averages.

But the Grizzlies' defense hasn't been up to snuff of late. The team gave up over 115 points per 100 possessions with Gasol on the court over the last five games, per NBA.com. That's not all his fault and Tony Allen has missed time, but as a Defensive Player of the Year award winner, Gasol has to share some of the blame.

Not only has Wall taken his passing to new heights this season, but he's starting to show signs of becoming a more efficient scorer. The lightning-quick point guard is shooting over 49 percent in December, which would be the highest shooting percentage in any month of his career. He has one more game to hold that number, and that comes Tuesday night against the Mavericks.

Wall's brilliance has the Wizards riding high with a 12-3 mark this month and a 22-8 record overall. The 22-8 start matches the best in franchise history.

It should never come as a surprise anymore when Lillard hits a huge shot. Lillard was at his clutchest in a thrilling comeback victory over the Thunder last week, scoring 40 points and nailing a game-tying three-pointer in the final seconds on a shot that was eerily similar to one he hit in the past:

Lillard went on to score seven points in the overtime. The 40-point performance was Lillard's second in a week and his slow first week of the season has been long since forgotten.

James has been mostly good this month, but his last effort was an all-time bad one for him: 17 points on 5-of-19 shooting with seven turnovers in a 23-point home loss to the awful Pistons. That embarrassment has sparked conversation about whether David Blatt is the right head coach, and now there's already a rumor that James might consider leaving Cleveland in the offseason.

Silly stuff to be sure, but that's where we're at right now. James is still a force of nature, but his efficiency is down this season and his defense has been abysmal. Happy 30th birthday, LeBron. Your gift is rumors about your future and a dip in the MVP Power Rankings.

10. Russell Westbrook (Previous ranking: 6)

Westbrook's numbers remain ridiculous. His PER is still over 32 and just below Davis. So why does he drop down to No. 10? Because Westbrook has been scuffling during crunch time. The electric point guard is shooting just under 40 percent in fourth quarters this season, and that number is under 30 percent in losses, per NBA.com.

As Westbrook has struggled in the fourth quarter, so has Oklahoma City. The Thunder have scored just under 102 points per 100 possessions with Westbrook on the floor in fourth quarters this season, per NBA.com. That's compared to a total offensive rating of over 110 with him on the court.

Getting Kevin Durant back will help, but Westbrook has to make better decisions regardless in crunch time.

Next 5: Blake Griffin, Klay Thompson, Chris Paul, LaMarcus Aldridge, Dwyane Wade