Quoted from ESPN NBA Rumors:
From Chris Mannix of Sports Illustrated:
"Guy I think would fit really well in Boston, if he wants to keep playing: Joel Przybilla. Defensive minded enforcer in the middle."
With the Celtics losing Shaquille O'Neal (retirement), Kendrick Perkins (trade to Oklahoma City) and potentially Glen Davis via free agency, they could indeed be looking for help up front.
So Przybilla presents himself as an option.
Other available big men the C's could potentially target include Samuel Dalembert (though he'll have other suitors and may be too pricey), Hilton Armstrong, Kwame Brown, Aaron Gray, Earl Clark and Kyrylo Fesenko.