The ultimate swing game?

The Boston Celtics are far too unpredictable to flatly declare that Game 6 of an Eastern Conference first-round series against the Atlanta Hawks is a must-win situation. The Celtics have had a way of making things as difficult as possible on themselves this season, yet have still found a way to survive more often than not.

It is fair, however, to note that the momentum of the series might have shifted with Atlanta's Game 5 triumph and that Boston would be well-served to take care of business with the benefit of home court on Thursday night at TD Garden.

Let's start with the positive news for the Celtics: Past history suggests that Boston is still in a favorable position. Since the NBA playoffs went to a 16-team format during the 1984 season, teams up 3-1 in series went on to win 94 percent of the time with only eight outliers in the bunch. Heck, teams up 3-2 have gone on to win 85.7 percent (209-35) of those series.

But here's where it gets daunting for Boston. In series tied at three games apiece, the home team has emerged 80.4 percent (86-21) of the time. The odds essentially flip-flop if the Hawks steal Game 6.

All of which suggests that Boston shouldn't mess around with Game 6.

It's that potential for a Game 7 on the road that seems to have left a bit of doom and gloom hovering over already rain-soaked Boston as the Celtics endured a quiet off day.

While the Celtics have largely been in control of this series, highlighted by a dominating effort in Game 4, it was the final seconds of Game 5 that showcased just how tenuous this matchup has been. If Al Horford doesn't prevent Rajon Rondo from driving the baseline in the final seconds of Atlanta's 87-86 triumph on Tuesday night, the Celtics might be in relaxation mode while awaiting a second-round opponent.

Instead, they'll have to grind out another 48 minutes. Or maybe another 96. Either way, things got more difficult when Boston couldn't complete the comeback Tuesday.

Maybe that's why Rondo sat at his locker for a long time before finally standing up to shower and later head to the podium to explain how he couldn't convert in the final seconds -- even though his clutch steal was the only reason the Celtics even had a chance to win at that point.

That the three games in Atlanta have been decided by an average of less than six points per game should put Boston at ease a little bit. The Celtics also split the regular-season games in Atlanta (nearly stealing a win with a reserve-heavy lineup late in the season). All of which is to say that they shouldn't be overwhelmed if there is a deciding Game 7 on the road.

But the fact of that matter is the complexion of the series shifted in Game 5. While Paul Pierce, looked hobbled for much of the night with his ailing left knee, the Hawks had their familiar starting five on the floor for the first time since January and got exactly the spark coach Larry Drew hoped the unit would provide.

Al Horford eschewed any talk of limiting his court time by providing 41 dominating minutes under the basket, converting Atlanta's final two baskets as part of a 19-point, 11-rebound effort. Sure, Horford and Josh Smith might be less than 100 percent themselves, but they are playing some incredibly inspired ball in spite of their ailments.

What's more, Marvin Williams came up big in his first game back in the starting lineup (15 points, including a trio of 3-pointers), while the Atlanta backcourt of Jeff Teague and Joe Johnson probably won't be as quiet as they were on Tuesday.

The Celtics were clearly frustrated at allowing this series to advance another game. After a dominating Game 4 effort, Pierce talked about not wanting to give Atlanta even the slightest bit of confidence. Before Game 5, the Hawks' Johnson was openly wondering about his team's ability to muster up the energy on the verge of elimination, but it's clear that Atlanta won't have any such issues from here on out.

Boston can take solace in having been in this sort of situation numerous times in recent seasons. OK, not exactly this situation, but something close to it.

Amazingly, nine of Boston's 12 previous playoff series in the Big Three era have seen the Celtics open a 3-2 advantage. Boston is a mere 4-5 in Game 6 of those series, but did prevail in Game 7 in three of those situations (losing in 2009 vs. the Orlando Magic and 2010 vs. the Los Angeles Lakers).

The difference this time around is that Boston doesn't have the luxury of Game 7 on their turf, something their regular-season success often afforded the past four years. Rarely have the Celtics endured a situation like this where they had to win to avoid heading back on the road. All that hoopla about allowing the Hawks to finish with a better overall record and steal home-court advantage might end up being a determining factor in this series.

Maybe the most comparable situation was the 2010 playoff run when Boston eliminated LeBron James and the Cleveland Cavaliers in Game 6 of an Eastern Conference semifinal series at TD Garden to avoid having to go play Game 7 in Cleveland. The difference then was that Boston had won twice on the road in that series, including a lopsided Game 5 victory.

This time around Boston has to put Game 5 in the rearview mirror. The Celtics are still in prime position to end this series and need not make this more difficult than they've already made it.