Since there has been a number of people throwing the "injury exception" option out there. This should clear it up:
From Larry Coon's NBA Salary Cap FAQ:
DISABLED PLAYER EXCEPTION -- This exception allows a team which is over the cap to acquire a replacement for a disabled player who will be out for the remainder of that season (if the player is disabled between July 1 and November 30) or the following season (if the player is disabled after November 30).
Approval from the league (based on a determination by an NBA-designated physician) is required for this exception to be used.
Teams sometimes have had difficulty getting the NBA to approve an injury exception. For example, Danny Manning tore an ACL toward the end of the 1997-98 season, yet the NBA did not approve the Suns for this exception. More recently, the Magic did not receive this exception in 2003 for Grant Hill. However, this exception was granted in the 1999 offseason to San Antonio, so they could replace Sean Elliott, who was disabled due to kidney problems. This exception was also granted to Charlotte soon after Bobby Phills was killed.
From our own Roy Hobbs in the comments section:
If the league approved an exception, we would have to use it next year, since the injury / surgery occurred after November 30. So, if the NBA approved the exception, we’d basically a $3 million exception to spend on somebody next season, but nothing for this year.
Also, I don’t think we’d be allowed to go over the 15 player roster limit, even if we were given an exception. Rather, we’d have to apply for a separate exemption from the NBA. Those roster exemptions are exceedingly rare, and are usually only given when a team loses multiple / several players for the season.
As you can see, the NBA doesn't just hand these exceptions out. They are very hard to get granted. Jermaine O'Neal's case is definitely not one that is going to get granted -- the Celtics wouldn't even try.
In order for it to happen, the C's would have to prove that if O'Neal had surgery next week, he'd not only miss the rest of this season, but the rest of next season too.
O'Neal has already stated that if he did get surgery, he would be back around the end of the regular season / beginning of postseason. He also said that he would be fully healthy next season with the surgery.
So the injury exception is not an option.
Let's be clear on one thing: The only reason O'Neal hasn't gotten surgery yet is because the Celtics are a legitimate championship contender. It's apparent that the swelling is not going to go away, and it's something that, if he chooses to, he will have to deal with until surgery in the offseason.
If he's playing on a team with no shot, he's under the knife by now. O'Neal badly wants to be a part of this team's success, and he's struggling with the decision solely because of this. If he opts out of surgery, he's essentially putting his career (and future health) on the line for this season. At the same time, this is why he came to Boston -- for a shot at the title.