In today's PER Diem column , ESPN.com's John Hollinger examines the chances of a team rallying from a 3-1 series deficit in the opening round of the postseason (only eight teams have ever done it since the 1984 season, but a whopping five teams have the possibility this year). A look at his take on whether the Hawks can pull off the rather improbable against the Celtics:

The Hawks won Game 5 at home against the favored Celtics, and we might not read much into a one-point home win except for the circumstances. The Hawks have played basically the entire season without All-Star center Al Horford, but he returned last night and invigorated Atlanta with 19 points and 11 rebounds.

The Hawks have shown they can compete in Boston -- even without Horford, two of their three games there this season went to overtime. Also, as I discussed last night, it would be the most Hawks thing ever to win Game 6 in rousing fashion and then come home and lose by 25 in Game 7.

Horford gives them just enough offensive competence to pose a threat to Boston. The Hawks have struggled all year, and really all throughout the Joe Johnson era, against elite defenses. Boston in particular gives Johnson fits. After he destroyed them single-handedly in Game 4 of the first round in 2008, the Celtics basically decided that somebody else would do the damage from now on, and have loaded up on Johnson ever since.

Johnson's slow decisions with the ball and the coaching staff's willingness to iso-Joe themselves into oblivion have helped prevent Atlanta from having much success against the Celtics offensively, but Horford's return (and Josh Smith's return, after he missed the end of Game 2 and all of Game 3) provides hope they can score more consistently.

And they don't need to score a ton. Here's the dirty little secret about the Celtics that most everybody overlooks: They stink at offense. Boston was 24th in Offensive Efficiency in the regular season at 98.9 points per 100 possessions, putting it right between New Jersey and Toronto. Every other playoff team was above the century mark. In the playoffs, against a team with no center (and no bigs whatsoever in one of the five games), the Celtics have been worse: just 94.7 points per 100 possessions.

Thus far they've survived by strangling the Hawks' offense; Boston leads all playoff teams in Defensive Efficiency. But if Horford can make the Atlanta offense merely below-average rather than awful, the Hawks can do this.

Not that they're likely to, mind you: AccuScore gives Atlanta just a 17 percent chance, partly because their model favors Boston's experience. But the Hawks are no strangers to the playoffs anymore, and the franchise's almost supernatural ability to make the second round of the playoffs before flaming out (15 times in 41 years) gives it an odd slice of history in its favor.

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