The Boston Celtics signed center/forward Sean Williams on Friday and subsequently waived injured center Jermaine O'Neal.

Williams, the 17th overall pick in the 2007 NBA Draft, averaged 4.3 points and 3.6 rebounds in three seasons with the New Jersey Nets before being waived in January 2010.

The 6-foot-10 Boston College product appeared in eight games for the Mavericks this season, last seeing action on March 19 against the Nuggets.

O'Neal underwent season-ending surgery on his left wrist last month.