Doc and Danny are cagey about this, but a recent article by Forsberg quotes them in such a way that makes it sound like the three players the Celtics were targeting with their pick were (
http://espn.go.com/blog/boston/celtics):
Jimmy Butler
Reggie Jackson
JaJuan Johnson
Once Reggie Jackson was off the board, it narrowed to two (JJ and Jimmy) and they pulled off the trade with the Nets figuring that even if JJ was picked by Dallas (who had the pick in between), that Jimmy Butler would still be available.
Interesting read.