Celtics Long Time Rebounding Issues Fixed?

Since 2010 when center Kendrick Perkins was traded to the Oklahoma City Thunder, the Boston Celtics had issues grabbing rebounding. For the last few seasons Boston finished near the last in rebound efficiency and percentage. This season Boston is currently averaging 56.4 rebounds per game, good for 4th in the league. So what changed?

Physical Bigs

The additions of Aron Baynes and Daniel Theis have proven to be excellent decisions. Both centers are not afraid to get physical down low and with for loose balls. Also they have a better understanding of the techniques of boxing out and getting into position, which is something Celtics have lacked over the years.

Team effort

Everyone is crashing boards... everyone. Horford (8.7), Brown (6.9), Baynes (6.0), Tatum (5.8) and Rozier (5.4) all are contributing. 

Size

Length is definitely a factor winning rebounders as this year the Celtics are way bigger and taller at all positions.