From the moment Danny Ainge made the decision to bring back the core of last season’s Celtics  team that made it to Game 7 of the NBA final and then add veteran centers Shaquille and Jermaine O’Neal  to the roster, the Celtics knew that health was going to be part of their story this season.
They were already beginning the season with their then-starting center Kendrick Perkins  recovering from knee surgery and it didn’t take long for injuries to Jermaine O’Neal to become an issue in training camp. From there it’s been one thing after another from Delonte West  missing 39 games with a fractured wrist to Marquis Daniels ‘ frightening spinal cord injury and including everyone from Kevin Garnett  (briefly) to Von Wafer .
And yet you can make the case that the Celtics have actually been somewhat fortunate. The only two players who have avoided injuries that led to misses games this season have been Paul Pierce  and Ray Allen , which is rather remarkable when you consider their age and regular dose of 36 minutes a night. Additionally, Garnett missed just nine games with a strained calf muscle and Glen Davis  has had to sit just four games because of a knee problem. Rajon Rondo  missed a dozen games due to various leg and finger problem, but most teams would take a net loss of 25 games to their five most important players.
Kevin Pelton from Basketball Prospectus  did some amazing leg work on injuries throughout the NBA. He found that while the Celtics had the third-most missed games due to injury with 233 (behind Milwaukee and Portland), and the second-most minutes lost in terms of rotation players, the cumulative impact of those injuries dropped from what can be called, “catastrophic” to something like, “significant.”
In other words, the Celtics have been both lucky and unlucky with their health this season. While the amount of missed games has been overwhelming both in games and practices, their big four (and Davis) have been available almost every night. All of that helps explain their very good, but not great, 54-23 record at this point.
Here’s how the injuries have broken down this season:
Time missed: 9 games (10 if you count the majority of the Pistons game he missed when he injured his calf).
Record without him: 6-4 or 6-3 in those nine games he was inactive.
Quick take: The Celtics followed a familiar pattern of holding down the fort without Garnett, as they have done over the last four seasons. In his absence, Glen Davis became the starting four and that showed just how valuable he is to the bench, and how much more effective he is in a combination role where he plays both forward and center. They survived, but hardly prospered.
Time missed: 12 games
Record without him: 8-4
Quick take: Two things happened that allowed the Celtics to get by without Rondo. First, Nate Robinson  had some terrific games as the starter earlier in the season. Second, when Robinson faltered, Paul Pierce had a good run as a point-forward. The Celtics have had bigger problems in games that Rondo played but didn’t perform well, although injuries played a part in that as well.
SHAQUILLE O’NEAL 
Time missed: 40 games
Record: 26-14 (16-12 since the Achilles injury in early February).
Quick take: The Celtics were able to survive the first dozen games O’Neal missed with various foot and leg ailments, going 10-2 over a couple of three-to-five game stretches. The Achilles injury, on the other hand, has had a much more significant impact. Ainge expected Shaq would be back shortly after he made the Perkins trade, but days became weeks, weeks became months and they still don’t know if he’ll be back and how much he’ll be able to contribute for the playoffs.
Games missed: 43
Record without him: 33-10
Quick take: Of all the reasons for making the trade, the Celtics’ record without Perkins provided the most basic logic behind the deal. There were other factors as well — the long-term health of his knee, the question of re-signing him — but Ainge went through with the move on the basis that they performed better in his absence than when he was on the floor. The health of the O’Neals will go a long way toward determining the ultimate outcome of the trade.
Games Missed: 56
Record without him: 41-15, or 13-8 with him
Quick take: When Shaq was playing — and playing well — the other O’Neal was a luxury. When Perkins came back, he had time to get knee surgery. Now, Jermaine O’Neal has become a necessity and how he holds up may hold the key to the Celtics playoff fortunes.
Games Missed: 57 (10 due to NBA suspension)
Record without him: 42-15; 12-8 with him
Quick take: While “Just wait until Delonte comes back” has been a rallying cry this season, the Celtics actually played well in his absence. Still, when he wasn’t in the lineup the Celtics were forced to play Robinson too many minutes at point guard and it also left them without a veteran backup shooting guard behind Ray Allen for most of the season. They are a better team with West than they are without him.
The other significant injury that affected the Celtics was the loss of Marquis Daniels to a spinal cord ailment. At the time, the Celtics were 37-12 and ahead of the pack in the East. Without Daniels, the Celtics lost their one true backup wing player and opened the door to the Perkins trade. The Celtics still don’t have a wing defender as good as Daniels, although Green is an upgrade offensively.
All that said, the Celtics are healthier than they’ve been in months. For the first time since the early days of the season, they had 14 of their 15 players available for practice this week and they had healthy players on the inactive list for their game against the Sixers.
The two questions are whether Shaq can come back for the playoffs and if they can maintain their health for the playoffs. The fact that they have been able to get consistent production and minutes from Garnett, Pierce and Allen is the biggest reason for optimism heading into the postseason.