PER Diem: April 23, 2009


We're two games into the playoffs, and already we can break down the eight series into two groups: The three "95 percent" series and the five "50 percent" series.

First, the 95 percenters -- based on history, Cleveland, Denver and the Lakers each have at least a 95 percent chance of advancing to the second round, and having watched their series so far, that number seems low.

I say this for a couple of reasons: (1) Teams that win the first two games of a best-of-seven series win about 90 percent of the time; and (2) teams that are seeded first or second have won 93 percent of first-round series since the league expanded to a 16-team format, and have won every series but one (Golden State's 2007 upset of Dallas) since switching to a best-of-seven format.

Further, of the teams seeded first or second that lost, all but one dropped at least one of the first two games at home. So for the Lakers, Cavs or Nuggets to lose their series would be virtually unprecedented -- only the 1994 Nuggets, who beat top-seeded Seattle after dropping the first two games in a best-of-five series, managed to overcome a 2-0 deficit as a No. 7 or No. 8 seed.

Thus, pencil in the Lakers, Cavs and Nuggets for Round 2. Heck, use a Sharpie if you want.

As for the other five spots in the second round? Those are pretty much up for grabs.

Let's look at some historical trends here for series tied 1-1.

In first-round best-of-seven series, road teams that earned a split in the first two games have won only five series in 15 tries -- a surprising record of failure to take advantage of their newfound home-court advantage.

But if you throw out all the series involving No. 1 and No. 2 seeds, that record improves from 5-10 to 4-4, which puts us back into toss-up land for four of the five series that are tied in this postseason. And you can argue that the Chicago-Boston matchup belongs there, too, given that the Celtics' injury situation makes them far less imposing than a typical No. 2 seed.

Let's delve a little deeper. First of all, there's an interesting story here with scoring margin. Of the 15 series that were tied 1-1, the visiting team had been outscored in the first two games in 14 of them; in the one exception, the visiting team had only a plus-1 advantage.

But this year, we have one road team with an enormous point differential: Houston is plus-23 after the first two games. The four other situations are more typical: Dallas is minus-13, Miami is minus-11, Philadelphia is minus-7 and Chicago is minus-1.

Since our sample size of first-round best-of-seven series is limited, I expanded the lens to take in best-of-seven series from any round in the past 15 years, giving us 20 cases to look at in which the road team outscored the opponent while splitting the first two games. And after adding those in, we see immediately that scoring margin is important.

The road teams that were ahead in point differential after two games went on to win the series 11 of 20 times, and in only two of the 20 cases were they eliminated before Game 7; in both of those cases, they were playing against Michael Jordan.

So good news, Rockets fans: Based on NBA history, there's about a 90 percent chance that, at worst, your team will be playing a seventh game in Portland, and there's a better-than-even chance that Houston will win the series.

As for the other four teams, the news isn't encouraging. Teams that trailed in point differential after two games went on to win the series just 10 times in 28 tries, or a little better than one in three. Even teams with a very small negative scoring margin lost a disproportionate number of times.

So, as we sit here today after just two games, odds are that we'll have two lower-seeded teams advancing to the second round. The percentages say that Houston will likely be one of those teams, and informed speculation suggests that Dallas or Chicago will be the other. (My apologies to Sixers and Heat fans, but I'm just not feeling it just yet.)

But wait, we're just getting started. All of these odds will shift dramatically once the final whistle blows in Game 3. In fact, the winner of Game 3 takes the series 75.8 percent of the time after the two sides split the opening pair of games. And of course, the five teams that started on the road will all have home-court advantage for this pivotal contest.

All of which sets up a very interesting quintet of games heading into Thursday night and the weekend. The Lakers, Nuggets and Cavs may be set to cruise into Round 2, but we have only a fuzzy idea about which five teams will be joining them.

In fact, even the historical odds are less telling than we might think. The difference in probability between 1-in-3 (for Dallas, Philly, Chicago and Miami) to approximately 3-in-5 (for Houston) is a big deal, yes, but when you're dealing with a single series, as opposed to hundreds, it leaves a lot of room for randomness to come into play. The same goes even after Game 3 -- the door is still open, as there is a 1-in-4 chance for the trailing team to come back and win.

So let me leave you with this caveat: If we played this out several hundred times we'd get Houston in Round 2 more often than not, and a random assortment of one or two of the other four teams joining them. But that isn't what we're doing here -- it's a single observation, and flukes can and do happen. So we could end up with no upsets, or we could end up with five.

But if we're looking strictly at percentages, we'll have two upsets, and there's a better-than-even chance that Houston will pull off one of them.

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