On Wednesday the Celtics will reach the midway point of their season and about the only thing we know for sure at this point is that they are not as bad as they’ve been in 2009, and they weren’t as good as they were at the end of 2008. In other words, the Celtics are somewhere between the Jordan-era Bulls and the every-era Clippers. Despite that wide range, it’s presumably safe to say that the Celtics are a likely 60-win team and a serious threat to repeat as NBA champions, but what seemed like a three-team league as 2009 began now has a half-dozen teams that see themselves as viable contenders. 

This is great for the NBA, if not for the guys in the green. What was once a six-month wait until Cavs-Celtics and then the Lakers in the Finals has now turned into a real competitive regular season. As much fun as everyone has wondering where LeBron James, Chris Bosh, Dwyane Wade et al will wind up in 2010 it is much better for league business to have the attention focused on the court.  

So let’s have at it, player by player. We start with the starters, which seems like a logical place to begin. Quick quiz: Would you trade the Celtics starting five for anyone else’s in the league this year? (No cheating by saying you’d trade everyone in the league for LeBron). The honest answer is no. From Rajon Rondo to Kendrick Perkins with three Hall of Famers in between, the starting five is the best, most complete, most together unit in the league. That’s the good news.

Rajon Rondo: If Rondo isn’t the best point guard in the East, then he’s in the top three. Flash back to the start of 2007-08 season and say that again slowly. For all the concern about what Rondo can’t do (make a 15-foot jumper) it’s tempting to forget what makes him so good. 

He is a fantastic passer with a 3-1 assist-to-turnover ratio, a great rebounder and one of the best on the ball defenders in the league. No one in the league can stay in front of him and he’s still just 22 years old. Here’s the problem: Other teams have begun to figure out that if they can stop Rondo they don’t have to worry so much about Ray Allen, Paul Pierce and Kevin Garnett. That’s a hefty burden to place upon his shoulders, and he has struggled with it the last few weeks. 

It might be going too far to say that he is the key to the rest of the season, but not by much. After all, the Celtics did win a championship with Rondo neutralized in two playoff series last year. But if Rondo can’t figure it out, or if the Celtics can’t come up with a viable second option (be it Sam Cassell or Stephon Marbury or Gabe Pruitt), then it might be a one and done for the Celtics. He is that important. 

Ray Allen: The consummate professional is having an excellent season… almost exactly like the season he had last year with one huge exception. Allen is shooting the lights out inside the 3-point arc which has bumped his field goal percentage up to around 50 percent. 

Statistically his 2008-09 is looking an awful lot like his 2007-08.  Still, he has said that he feels more comfortable this year and that is no small thing for a player who relies on routine and rhythm as much as Allen. Guaranteed he will go through a tough stretch at some point in the second half, and guaranteed people will begin to write his basketball obit. Allen has earned better than that in his year and a half in Boston. 

Paul Pierce: In November, Pierce was being talked of as an MVP candidate after he put the team on his back and won a couple of games with magical fourth quarters. In December he struggled to shoot 40 percent. Lately, Pierce has been awesome again, so what gives?

Pierce seems to have achieved some sort of inner calmness after winning the championship and the Finals MVP last year. He’s not playing like he has something to prove to the rest of the league, rather he is content to ride with the flow as he calls it. Pierce has resisted the urge to do everything by himself, and there must have been times in the last few weeks when that looked like an enticing proposition. 

Witness his huge jumper against Toronto on Sunday. It was only his second shot of the fourth quarter, a quarter in which he went wire-to-wire. The key question for Pierce is health. Can he stay fresh logging 38+ minutes a night?  

Kevin Garnett: KG was great in 2007-08. How great? According to the guys who do the adjusted +/- stats for 82games.com, Garnett was the best player in the league last year and by a wide margin. 

In a career full of unrecognized greatness, Garnett’s first season with the Celtics might have been even better than his 2004-05 season when he dominated the league and finished 11^th in the NBA MVP voting. Garnett has not been as good this season. Part of it may be Doc Rivers carefully keeping his minutes in the 32-minute range. Part of it may just be the effects of playing 108 games in 2007-08. 

But Garnett is still very, very good. The key is keeping him fresh for the playoffs, something that becomes much harder if the Celtics can’t get productive play from the bench. 

Kendrick Perkins: Rondo gets all the ink for his improved play—and justifiably so—but Perkins has also made a nice little jump this year. His shooting is down a touch as he expands his range beyond dunks and put-backs, but a few field goal percentage points is worth the effort. Remember that Perkins is still only 24 years old. 

He is becoming a very good defensive player who works exceptionally well with Garnett against the other team’s bigs. He also seems to have curbed his tendency for picking up technical fouls. Two obstacles still remain for him: Avoiding cheap offensive fouls when he sets screens and improving his free throw shooting. 

Now we come to the crux of the issue. The bench. 

In hindsight, the decision to not resign James Posey now looks like a major mistake. Yes he might be a shell of himself by the time he gets to that fateful fourth year of his contract, but this team has a three or four-year window and an argument can be made that Danny Ainge should have done everything to maximize their chances in the here and now and worry about tomorrow when tomorrow comes. 

The bench has a couple of major issues: Ball-handling, 3-point shooting and height. In the abstract, Eddie House, Tony Allen, Leon Powe and Big Baby Davis all contribute positive things, but in practice, they constitute a mismatched set. 

House is not really a point guard, Allen who everyone unfairly wants to blame for everything is simply not Posey and Powe and Davis are often too small to play in tandem against big front lines. Let’s take them one at a time. 

Eddie House: House is like the Bizarro-world Rondo. As with Rondo everyone worries about what Eddie can’t do, but unlike Rondo, the one thing he can do is make outside shots. The problem is that he hasn’t made enough of them. 

If the Celtics can find an effective backup point, House can get back to doing what he does so well, knocking down 3-pointers. Until then, he is the Celtics best option behind Rondo and the man gives you everything he has. 

Tony Allen: On Saturday during the Mut-and-Bradford show, Jess Camerato and I took calls for an hour and the reasons suggested by the callers for the Celtics struggles boiled down to Tony Allen,  Tony Allen, and oh yeah, Tony Allen. 

Allen can be a nasty one-on-one defender, but he too often goes for fakes and gets himself out of position. He can be an explosive threat going to the basket, but he’s just as likely to dribble the ball off his leg. It’s even possible that he will do all four of those things within the span of two possessions. 

All of that makes him a convenient target for people who say he’s not cerebral or intelligent or what have you, and that’s not entirely fair. Allen can be a very useful piece of the bench, but one thing he is not is Posey, and the biggest issue Rivers has with the bench is the loss of versatility that Posey supplied. Where once they could go small, or big, now they can really only go small or normal, which is a problem because the backup bigs aren’t so big. 

Leon Powe: Like everyone else on the bench, Powe brings a certain skill-set that too often is limited by the inherent shortcomings of those around him. He is the Celtics best low-post scoring option off the bench, but other teams can take it away because the second unit lacks a creator and an effective shooter from the wing. 

Powe is also prone to the occasional defensive lapse, which causes Rivers to not trust him for very long. In the first month or so of the season Powe was a legit candidate for Sixth Man of the Year. Now, not so much. 

Glen Davis: Speaking of strange seasons, Big Baby has become a jump shooter, and not a particularly good one at that. Part of that (again) is because of the lineup around him. Powe is the better low-post option so Davis moves outside. He is capable of playing terrific defense on occasion, and he is so quick off the floor that he gets a number of offensive rebounds. 

But until he learns how to finish consistently, he remains an undersized, but active, role player.  

The Rest

Gabe Pruitt: Like what we’ve seen, but haven’t seen enough of it. It’s possible that Pruitt can be the answer to the second unit’s ballhandling issues, but he and House make for an awfully small backcourt. 

Brian Scalabrine: He’s not the 12^th man, so by definition shouldn’t Patrick O’Bryant be getting the Terry Duerod cheers? 

Scal just does what Scal does. He moves without the ball, plays fundamentally smart, if not physically imposing defense, and generally is in the right place at the right time. If he could only make a jump shot more consistently… 

Patrick O’Bryant: He came to the Celtics as a two-year project and he is still a project. O’Bryant has shown flashes—a nice scoring touch, shot-blocker instincts—but he hasn’t shown enough in practice to warrant more of a look. Rivers says he is improving in that department and maybe it’s time to see what he can do for a few minutes. 

Sam Cassell: Says he’s ready. Still has more technicals than minutes played. 

Bill Walker: Has at least played, and has legitimate small forward size. 

JR Giddens: Lit it up in the D League.   

The Celtics have fallen from their perch as undisputed kings of the Eastern Conference, but they are still the co-favorites along with the Cavaliers. (Orlando still has to prove it.) The way the playoff situation is breaking down, finishing out of the top spot might not be the worst thing that ever happened to them since they could potentially avoid a Pistons or Hawks matchup, but they put such an emphasis on winning home court that it would be a huge mental downer to surrender the Number One seed.

That will be the key challenge for Doc Rivers in the second half. How much does he ride the starters to try to get homecourt if the bench doesn’t pick up the slack? The schedule eases up a bit after January (there is still one ridiculous stretch of five games in seven days in mid-March), and Rivers will have time to get back to basics on the practice floor. 

The key question for Ainge is: Does he make a move? The roster options are limited. Without a big expiring contract on the books, the move, if one is made, will likely have to be for a street free agent, which is why there has been such an emphasis on Stephon Marbury and trying to unretire PJ Brown. 

With 40 games behind us, in many ways the Celtics season begins now. 

Paul Flannery is a regular contributor for WEEI.com. He can be reached at pflannery@weei.com.