The numbers tell the story for the Celtics' disastrous frontcourt

If you want to know the primary reason that the Celtics find themselves in a somewhat surprising 1-3 hole to start the season, look no further than the drastic underachievement of their big men.

Here's a look at their stats through the first four games:

Tyler Zeller

TZ is averaging 4 points on 37.5% shooting, but that's not the worst part.  The man is seven feet tall and is averaging less than a rebound per game.  To put that in context, Celtics' 6'1" rookie guard Terry Rozier had more rebounds in his six minutes of play on Wednesday night in Indiana than Zeller had the entire first week of the season.

Zeller's sudden inability to rebound has landed him on the bench for the time being.  He's played the third least minutes on the team so far, ahead of only Rozier and Jordan Mickey.  On Wednesday night in Indiana he played only three minutes, going scoreless and grabbing one board.

Kelly Olynyk

Kelly Olynyk is edging out Zeller in the rebound category with a slightly less embarrassing 3.7 per game.  Offensively, however, Kelly has been the Celtics' worst player.  His points per game average matches his rebound average (3.7) and he's shooting an atrocious 22.2% including 10% from three.

Olynyk also rode the pine on Wednesday night, sitting the entire second half after finishing the first with no points and two rebounds in 10 minutes.

David Lee

So far Lee hasn't been the scorer/rebounder that we thought he would be, averaging just 6.5 points per game on 34.6% shooting to go along with 6.3 rebounds.

Fortunately, Lee looked good Wednesday in his 18 minutes off the bench.  He shot 4-6 from the field on his way to 10 points and 6 rebounds, leaving some to question why Brad Stevens didn't play him more.

Jared Sullinger and Amir Johnson

Jared Sullinger and Amir Johnson have been solid for the most part.  Although neither of them have an eye-popping stat line, they've at least managed to keep their field goal percentage up around 50%.  Sullinger leads the team with 7.3 rebounds per game and Johnson leads all Celtics' big men with 9.5 points per game and a shooting percentage of 53.8%.

Unfortunately, Amir was called on to start against the Pacers and had by far his worst performance of the year.  He played 20 minutes but didn't manage to make a field goal, finishing with two points and four rebounds.

Sully also got the start, leading the bigs with 27 minutes.  He shot just 3-10 from the field on his way to nine points but he did manage to pull down 11 rebounds.

All in all, the Celtics' five big men have completely forgotten how to rebound.  Their number one rebounder so far is currently only the 49th best rebounder in the NBA.  Couple that with the fact that they have combined for only 32% of the team's total points this year, and only 21% of the team's points on Wednesday night against a Pacers team that doesn't exactly have a strong post presence since the departures of Roy Hibbert and David West.

It's hard to be too critical when we're only four games into the season, but so far the Celtics' frontcourt, which was expected to be their most improved phase of the game, has been their biggest weakness.

Follow Jack Bardsley on Twitter @BostonsBigFour

Photo Credit: Steven Senne/AP Photo via MassLive