Bumps in the road for the Big Four

Whether it's injuries, complacency or back-to-backs, the best teams in the league have hit some bumps in the road lately.

The Lakers lost big to the Cavs and Suns, and then needed another Kobe Bryant buzzer-beater to beat the shorthanded Kings. The Cavs looked like the best team in the league until they faltered at home on Sunday. Missing Kevin Garnett and Paul Pierce, the Celtics lost three straight before beating the Raptors on Saturday. And the Magic have been inconsistent all season.

The struggles don't stop there. Each of last week's top 14 teams lost at least once this week, and the top 13 went a combined 21-21.

There are some signs of life in the middle of the pack. The Grizzlies continue to play well. Since Nov. 14, they're 15-8, fourth best in the West and a game and a half better than the Nuggets. The Thunder and Raptors are also putting together some wins for the first time this season, and teams like the Bobcats, Bulls and Knicks are starting to creep up.

It all presents a cloudy picture in the Power Rankings. The top two still stand out, but the lines are pretty blurred after that.

• Last Week: Statement wins have Cavs on the move

Hero Team of the Week: Chicago (3-0)
Zero Team of the Week: Miami (0-3)

High jumps of the week: Philadelphia (+5), 4 Teams (+3)
Free falls of the week: Sacramento (-4), 5 Teams (-3)

East vs. West: The West leads 109-76 (0.589) in inter-conference games and was 10-7 this week.

Pace: Possessions per 48 minutes (League Rank)
Off: Points scored per 100 possessions (League Rank)
Def: Points allowed per 100 possessions (League Rank)
The league averages through Sunday are 95.4 possessions (per team) per 48 minutes and 103.8 points scored per 100 possessions.

NBA.com's Power Rankings are just one man's opinion and are released every Monday during the season. If you have an issue with the rankings, or have a question or comment for John Schuhmann, send him an e-mail. You can also follow him on twitter.

	TEAM (LAST WEEK)	REC.	BREAKDOWN
1	L.A. Lakers (1)	27-6	Pace: 97.5 (6), Off: 106.1 (11), Def: 98.2 (2) A team that spanked them in October was exactly what the Lakers needed on Saturday. And they exacted quite a revenge on the Mavs. But they lost Pau Gasol to another hamstring injury, more concerning than their recent offensive struggles.
2	Cleveland (3)	27-9	Pace: 93.0 (28), Off: 107.3 (7), Def: 99.4 (4) The Cavs were rolling (seven straight wins, 11 straight at home) until Sunday's loss, when they got to the line a season-low 13 times and allowed Charlotte to shoot 49 percent. After a grudge match with the Wizards, they're heading west again.
3	Boston (2)	24-8	Pace: 94.4 (22), Off: 106.8 (8), Def: 97.3 (1) The playoffs are more than three months away, but the injuries keep piling up and Kevin Garnett will be out longer than originally expected. The Celtics were still able to get an win over Toronto on Saturday without KG, Paul Pierce and Rajon Rondo.
4	Orlando (4)	24-9	Pace: 95.0 (14), Off: 107.4 (6), Def: 100.4 (5) Saturday's loss in Chicago ended a string of six straight games in which the Magic held their opponents to less than a point per possession. Chalk it up to playing the second night of a back-to-back? They've got three more in the next 10 days.
5	Portland (7)	22-13	Pace: 90.2 (30), Off: 106.5 (10), Def: 101.9 (11) Juwan Howard for Most Improved! The 36-year-old has two double-doubles, two more than he had in the last two seasons combined, and he's shooting 59 percent in five games as a starter. Despite their injuries, the Blazers have won eight of their last 10.
6	Dallas (5)	23-11	Pace: 94.8 (17), Off: 105.4 (12), Def: 100.4 (6) The Mavs may have established themselves as the second-best team in the West, but Sunday's game was evidence of a big gap between No. 1 and everyone else. They get another crack at the Lakers next week, but visit San Antonio for a test on Friday.
7	San Antonio (9)	20-12	Pace: 93.9 (24), Off: 108.2 (5), Def: 101.2 (7) The Spurs keep moving up the defensive rankings, but their offense took Sunday off in Toronto. After they host the Pistons on Wednesday, the schedule starts to get tougher, with the Mavs, Lakers and a four-game trip on the way.
8	Phoenix (11)	21-13	Pace: 98.4 (4), Off: 112.0 (1), Def: 107.8 (26) The Suns are the Jekyll and Hyde team of the week. They ended 2009 with big wins over the Lakers and Celtics, shooting 50 percent against the two best defensive teams in the league. Then they began 2010 by getting crushed by the Grizzlies on Saturday.
9	Atlanta (6)	21-11	Pace: 94.4 (23), Off: 109.9 (2), Def: 103.2 (13) On Tuesday at home, it was the Hawks' offense that couldn't get going. The next night in Cleveland, their defense couldn't get stops. The defense has been the greater problem as they've dropped five of seven. That's what separates them from the East's big three.
10	Denver (8)	21-13	Pace: 98.1 (5), Off: 108.6 (3), Def: 103.8 (17) A 'W' in Utah without Carmelo Anthony or Chauncey Billups is impressive, but the injuries have exposed a lack of depth and a defense that needs improvement if this team is to contend. The Nuggets' opponents have shot 49 percent since Billups got hurt.
	TEAM (LAST WEEK)	REC.	BREAKDOWN
11	Houston (10)	20-14	Pace: 95.7 (11), Off: 103.8 (17), Def: 103.7 (15) The Rockets closed out 2009 with a great win over the Mavs. They defended and they executed down the stretch. But then they began 2010 with just the opposite in New Orleans on Saturday, a reminder that this team is not very good on the road.
12	Oklahoma City (14)	18-15	Pace: 94.7 (19), Off: 103.0 (19), Def: 101.3 (8) With Saturday's OT loss in Milwaukee, the Thunder lost a chance to take sole possession of eighth, but their defense continues to be strong. Russell Westbrook has cut his turnovers down from 3.8 per game in October-November to 2.4 in December-January.
13	Memphis (15)	16-16	Pace: 96.3 (10), Off: 106.7 (9), Def: 108.1 (27) The Grizzlies were the most improved team from November to December, and they started January off with a blowout of the Suns. This week, they play the Blazers and the Jazz twice. If they can win two out of three, they must be considered a playoff contender.
14	Utah (12)	18-15	Pace: 94.9 (16), Off: 104.0 (16), Def: 103.2 (14) Tied with OKC and having lost both head-to-head matchups, the Jazz are now ninth in the West, with a home-and-home this week against 10th-place Memphis. Their offense has struggled (94.0 rating, 19.6 TO/G) as they've dropped five of their last eight.
15	Miami (13)	16-15	Pace: 93.5 (26), Off: 104.4 (14), Def: 102.6 (12) On another downswing, Saturday's loss to the Bobcats was definitely a low point for the Heat. They blew a 19-point lead to a team that had won one of its 15 previous road games. Now they've got the Hawks and Celtics, followed by a six-game trip west.
16	Toronto (16)	17-18	Pace: 95.1 (13), Off: 108.3 (4), Def: 110.0 (30) Jarrett Jack is filling in fine for Jose Calderon, averaging 12.7 points with a Calderon-esque 3.5 assist-turnover ratio as the Raps have won six of their last seven. If they continue to play the way they have, they'll shed that "Worst Defense in the League" tag soon.
17	New Orleans (18)	15-16	Pace: 94.5 (20), Off: 102.9 (20), Def: 105.9 (21) The Hornets lost, but David West broke out with 44 points in Houston on Tuesday to help the offense get going. Then they went and beat the Heat and Rockets at home. They're just 2-13 on the road though, and that's where they play 11 of their next 16.
18	New York (21)	14-20	Pace: 96.3 (9), Off: 104.0 (15), Def: 105.1 (19) Was Mike D'Antoni's decision to sit Nate Robinson for 14 games dumb or brilliant? Robinson's 41-point, eight-assists explosion in Atlanta on Friday is an argument for both sides. Now, Larry Hughes complains about playing time after a 43-point win.
19	Chicago (22)	14-17	Pace: 94.7 (18), Off: 96.6 (29), Def: 101.8 (10) The Bulls have won four straight, including Saturday's big one over the Magic. The D has been strong, and with Derrick Rose averaging 26.7 points in the last three, the offense is improved. They've also outrebounded 10 of their last 11 opponents.
20	Charlotte (23)	14-18	Pace: 93.1 (27), Off: 97.7 (27), Def: 98.7 (3) The Bobcats won more road games in the last two days (two) than they won in the first two months of the season (one). Now, they hold the eighth spot and play seven of their next eight at home, where they're 11-4 with a 92.9 defensive rating (vs. 104.1 on the road).
	TEAM (LAST WEEK)	REC.	BREAKDOWN
21	Sacramento (17)	14-19	Pace: 97.1 (7), Off: 105.1 (13), Def: 107.6 (25) The Kings have lost five of their last six, with Friday's loss to the Lakers ranking as easily the most heartbreaking game for any team in the league this season. Without their two best players, they were a Kobe buzzer-beating three from upsetting the champs.
22	L.A. Clippers (19)	14-18	Pace: 94.4 (21), Off: 101.6 (22), Def: 103.8 (16) The Clippers have won three straight and seven of their last 10 at home with a 99.2 defensive rating. They play seven of their next nine at Staples Center, but four of those seven are against the Blazers, Lakers (twice) and Cavs. They're 2-10 against our top 11.
23	Milwaukee (20)	13-18	Pace: 95.7 (12), Off: 99.3 (25), Def: 101.8 (9) The overtime period against OKC on Saturday was a nice time for Michael Redd to get hot, helping his team end an ugly 1-7 stretch during which the only win was over the Pacers by three points. Before that game, Redd had been shooting 33 percent from the field.
24	Philadelphia (29)	10-23	Pace: 93.6 (25), Off: 103.7 (18), Def: 108.2 (28) The Sixers finished their trip west by winning three out of four. They did it with offense, shooting 53 percent and moving the ball well in the three wins, though they shot blanks on Thursday in L.A. The defense still hasn't shown any improvement over 33 games.
25	Golden State (27)	9-23	Pace: 103.5 (1), Off: 102.4 (21), Def: 108.3 (29) When you play the Suns, Celtics and Lakers in four days, two out of three ain't bad. Anthony Randolph actually started four straight games before being put back on the bench for Saturday's loss in Portland. He's scored 10-plus in eight of his last nine.
26	Detroit (24)	11-21	Pace: 90.6 (29), Off: 100.0 (24), Def: 106.0 (22) The Pistons ended 2009 with a nine-game losing streak. They began 2010 with four days off to lick their wounds, but they've got a back-to-back in Dallas and San Antonio starting Tuesday. Charlie Villanueva is 16-for-66 (24 percent) over the last seven games.
27	Indiana (28)	10-23	Pace: 99.6 (2), Off: 98.2 (26), Def: 104.0 (18) The Pacers ended their eight-game losing streak with a win over the Timberwolves on Saturday, but Sunday's 43-point loss in New York has got to be the low point of the season, even if they were playing without Danny Granger and Troy Murphy.
28	Minnesota (25)	7-28	Pace: 98.5 (3), Off: 96.7 (28), Def: 107.3 (24) When you average 102 points over four games and lose them all by an average of 11 points, you had better take a good look at your defense. Losing to the Spurs, Jazz and Magic is acceptable. Giving up 122 points to the very shorthanded Pacers is certainly not.
29	Washington (26)	10-21	Pace: 96.8 (8), Off: 101.4 (23), Def: 105.5 (20) Off the court, the Wizards are in a whole mess of trouble. On it, they're not much better, having dropped four straight. Flip Saunders blasted his team's D after Tuesday's loss to the Thunder, but it didn't help much. The Spurs shot 51 percent on Saturday.
30	New Jersey (30)	3-30	Pace: 94.9 (15), Off: 94.6 (30), Def: 106.5 (23) Wednesday's win over the Knicks was probably the Nets' best W of the season (though they played better in a couple of early losses). All but Trenton Hassell's 17 minutes were played by guys under contract next season, so they have that going for them.