PER Diem: April 28, 2009

Injuries have been a dominant theme throughout this year's playoffs, but perhaps no series has been more affected by them than the tussle between Boston and Chicago. The loss of Kevin Garnett has allowed the Bulls to stay even with the defending champs through four games, while the absence of Leon Powe following Game 2 has further limited Boston's options in the frontcourt.

Meanwhile, Chicago has been operating without starting forward Luol Deng and now faces the prospect of playing without another high scorer on Tuesday. Though Ben Gordon has said he'll play despite straining his right hamstring in Game 4's double-overtime classic, it's possible he'll be too limited to contribute much.

With one game decided on a 3-point bomb, one in overtime and another in double overtime, the bar has been set pretty high for Game 5. The importance of the game is underscored by the fact that 83 percent of Game 5 winners go on to win the series. And how the two sides cope with their injuries is the game-within-the-game that's likely to determine the winner.

For Boston, the best way to deal with the injuries boils down to one single admonition: Its big men can't foul, because the Celtics have nothing in reserve.

Even though KG and Powe were out, Boston coach Doc Rivers' reluctance to use Mikki Moore in Game 4 was so obvious he might as well have been wearing a neon sign saying, "Mikki scares me!"

Moore played only six minutes in Game 4, and Rivers wouldn't let him near the court in the two overtimes, even when Kendrick Perkins had fouled out. Moore's stock has sunk to the point that in the crucial first overtime, Rivers decided he'd rather put in Brian Scalabrine, who hadn't played in two months and wasn't even on the team's active roster in last year's postseason.

In other words, Boston has effectively chosen to go down to a three-player big-man rotation, with Brian Scalabrine as No. 3. All of which is a roundabout way of saying that Perkins and Glen Davis absolutely, positively can't get in foul trouble, because the options behind them are so horrific.

So far they've done a great job of staying on the court, with Davis averaging more than 41 minutes a game and Perkins more than 35, but the Bulls may seek to attack them more in Game 5.

There's another weapon for Boston to consider: If Pierce can check either Joakim Noah or Tyrus Thomas with some level of success, it's a huge advantage for the Celtics, because they can go small with Pierce at the 4 when the frontcourt starters need a breather.

The Bulls would be all but forced to go to a zone defense or match the Celtics' lineup with four perimeter players. And if Gordon can't play, a smaller lineup would put extreme pressure on Chicago's own guard rotation, forcing the Bulls to turn to the likes of Lindsey Hunter or Linton Johnson.

As for Chicago, the questions start with Gordon: As in, can the Bulls score if he's unable to play or too limited to be effective?

The Bulls would presumably start Kirk Hinrich, play the three perimeter players (Hinrich, Derrick Rose and John Salmons) each 40 minutes or more, and supplement them with a dollop of Hunter or Johnson. We might also see a Tim Thomas cameo, depending on how things are flowing.

If Gordon isn't himself, that will put even more pressure on Rose, their rookie point guard, to deliver. He's done it in the two Chicago wins -- he had 36 points and 11 assists in Game 1, and 23 points and nine assists in Game 4 -- but in the two intervening defeats he was a nonfactor.

Moreover, Chicago's best play with Rose was a 1-2 pick-and-roll with Gordon that left him isolated against Boston's Eddie House. (Side note: Since I've been criticizing Bulls coach Vinny Del Negro throughout the series, I should point out that this play has worked well.) That isn't going to be as effective if Gordon isn't on the court, because it's his scoring prowess that forced Boston to switch defenders on the play.

Instead, Rose needs to figure out how to score against Boston's big men when he catches them in switches on pick-and-rolls -- something he did very well in the first game and very poorly in the past three. He should be able to blow by these players off the dribble, but they've been able to gamble because of his inconsistent midrange jumpers and have backed off him.

Chicago is likely to run a lot more plays like that if Gordon can't be a factor, and if Rose can get to the basket it will give the Bulls a great opportunity to pile up fouls on Boston's big men and get into the soft underbelly of its frontcourt rotation.

If so, Boston will be tempted to crowd the paint, deny Rose's penetration lanes and dare the Bulls to beat them from outside. But they'd better be careful, because the Bulls are a good shooting team even without Gordon. Hinrich (40.3 percent), Salmons (41.7 percent) and Brad Miller (41.1 percent) all shoot well from 3-point territory, and if Tim Thomas gets on the court, he can also stroke it (41.3 percent).

So it's clear the losses incurred by both sides will have a profound effect on their tactics, and the side that makes the better adjustments is likely to leave TD Banknorth Garden with a 3-2 series lead. I still like Boston to prevail, both in Game 5 and in this series. But to do it, the Celtics will need to overcome their shortage of frontcourt bodies and keep the Bulls' high-scoring guards at bay.

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