PER Diem: Feb. 11, 2009

After L.A.'s impressive 6-0 road trip that featured consecutive wins in Cleveland and Boston, I received several angry letters from Lakers fans who were miffed that their team wasn't in the top spot in the NBA Power Rankings.

Certainly, L.A. has a strong case. At 42-9, they have the league's best record, and after last week they now own season sweeps against both the Cavs and Celtics. Yet the Lakers are third in the rankings this morning, behind Boston and Orlando.

So I suppose I should explain why they ended up there.

The most important reason is that the NBA Power Rankings use point differential rather than win-loss record. There's a good reason for this: point differential is a better predictor of future success, and thus a more reliable barometer of a team's quality. The Lakers have the league's best record, but rank third in point differential -- Boston and Cleveland are ahead, and Orlando is just a 10th of a point behind in fourth.

Ah, but don't the power rankings weigh more recent results more heavily? And could any team claim to have more impressive recent results than L.A.?

Yes, the rankings weigh the most recent 25 percent of games more heavily than the other games played, and that window includes the Lakers' wins in Boston and Cleveland. It also includes a loss at home to Charlotte, one that had dropped the Lakers to a distant fourth in the rankings two weeks ago.

In fact, over the past 12 games, L.A.'s point differential is inferior to both Boston's and Orlando's. And despite playing Boston and Cleveland, the Lakers played so many bottom-feeders that their overall strength of schedule during that period is worse than both Boston's and Orlando's as well.

Finally, home-road differential also works against them a bit. With 28 home games and only 23 games played on the road thus far, only Memphis has a bigger home-road disparity. It's a minor factor in the grand scheme, but it does work against them.

So, for now, the Lakers are third. I should point out that we're dealing with some pretty small margins here, as we have with the top four spots all season -- only two points separate first from fourth, compared to the yawning four-point gap between fourth and fifth. And, of course, No. 2 Orlando is likely to slip given the absence of Jameer Nelson (the power rankings don't factor player injuries).

But if you're evaluating the overall body of work through the season's first 50-plus games, it seems fair. Yes, L.A. swept No. 1. Boston; on the other hand, they also were swept by No. 2 Orlando. Not much separates the league's top four teams at this point, but if I have to rank their performance to date, putting L.A. in the third spot hardly seems an injustice.

John Hollinger writes for ESPN Insider. To e-mail him, click here.