Michael Lee of the Washington Post reports that the Celtics initially offered Fab Melo to the Wizards in the Jordan Crawford trade, but Washington preferred to take Collins and Barbosa and save more money going forward:

According to a league source, the Celtics offered Fab Melo, a 7-foot rookie from Brazil who appeared in just four games this season. The Wizards, though, had no interest in taking back salary beyond this season, especially for a big man who remains a project. They opted for the financial savings instead.