Robinson was a member of the Celtics for parts of 2009-10 and '10-11. He averaged 5.8 points for Denver this season a year after tearing his ACL.
Nelson was the 20th overall pick by Denver in 2004, only to have his rights traded to the Orlando Magic in a draft-night deal. He's averaged 12.3 points and 5.3 assists with Orlando, Dallas and Boston.
Nuggets general manager Tim Connelly said Nelson's ''veteran leadership will be of value to our team.''